I REALLY DON'T want to get into why I think Spinoza's philosophy was fundamentally wrong-headed, but here goes.
Spinoza's faith in the ability of mathematics to represent an absolute view of nature and that ideas are capable of presenting an absolute view of reality are certainly naive and, in one of the greatest achievements of 20th century physics, rightly viewed as being wrong on the evidence. Those are two of the cornerstones of the rickety cathedral of materialist-atheist-sceintism without which that structure can't be propped up. I think the extent to which science "works" for all too human purposes is often based as much on luck as it is on the efficacy of scientific method and mathematical correspondence to what is observed through science. As I have been pointing out in writing online for going on twenty years, the boneyard of discontinued science is enormous and mentioning its contents is forbidden. There are even huge bodies of formerly held to be reliable scientific truth long ago relegated to it which come back to life after the succeeding ideology within science is found to be inadequate. The suppression of Lamarckian inheritance in the hegemony of the modern Darwinian synthesis of natural selection with an early, now quite naive view of genetics appended to it, has come somewhat back to life recently. If the same turns out to be true in cosmology with the recent discovery of those very early galaxies that, according to what we were told was reliable cosmology and physics shouldn't have existed then overturning Big Bang cosmology, it's quite too early to know and the many materialist-atheist-scientistic declarations to that effect would seem to me to be rather premature. If there's anything the history of science shows, it is how thoroughly caught up in atheist religous ideological campaigning it has been. I would say that was true from the start, certainly as the 17th century wore on, in no small part due to the ideological claims of Spinoza and his admirers.
I am skeptical of the holy card view of Spinoza that is the common received wisdom of college-credentialed People of my generation. I remember it was with that ignorant and received feeling of sanctity that I opened a book by him, I think it was the Ethics, and was immediately skeptical of his Euclidean approach to the topic. I also looked at his Tractatus and was put off by his approach in many ways. Looking at that in preparation to answering this, I think he had definite issues with being Jewish - why his calls for the civil government of Holland to suppress the Jewish religion is better than the edicts of Ferdinand and Isabella in Spain doing that, I'd like someone to explain to me. I think he was too impressed with his own cleverness and too reliant on an uncritical use of the primitive science of his time, of what he had available as classical "history" and myriad other contents of his arguments to find him very useful, today. He was certainly not stupid enough to realize that the suppression of the Jewish religion would have been accomplished with violence and killing when Jews resisted that, he, his family history with the expulsion from the Iberian peninsula would have informed him of that fact.
The presentation of him as a martyr to reason and science is even more overblown than the fictional presentation of Galileo as the same. It's a romantic use of someone who obviously liked to piss people off and who didn't do that badly for himself, considering how he cut himself off from his family and community. That he supported himself without difficulty and did his writing and corresponded widely with many eminent people shows he was hardly a martyr - he died of natural causes, one source I looked at suspected silicosis from his profession of lens grinding was at least a contributing factor in it. If he died for science, it was a suicide.
In the first part of his Theologico-Political Treatise he was quite willing to mock all kinds of people and their beliefs as baseless and a product of their imaginations when what he deified "reason," natural law, etc. were as much a product of human imagination as idol worship and the propitiation of gods as a means of getting what we want. In looking at it again after so long it strikes me as being pretty naive. One of the more incredible passages early in the book to anyone who lived through the last part of the 20th century contains a typical claim of materialistic-atheistic-scientism:
(16) This element of inconsistency has been the cause of many terrible wars and revolutions; for, as Curtius well says (lib. iv. chap. 10): "The mob has no ruler more potent than superstition," and is easily led, on the plea of religion, at one moment to adore its kings as gods, and anon to execrate and abjure them as humanity's common bane. (17) Immense pains have therefore been taken to counteract this evil by investing religion, whether true or false, with such pomp and ceremony, that it may rise superior to every shock, and be always observed with studious reverence by the whole people--a system which has been brought to great perfection by the Turks, for they consider even controversy impious, and so clog men's minds with dogmatic formulas, that they leave no room for sound reason, not even enough to doubt with.
First, I would guess that what he, sitting in Holland, knew of "the Turks" was hardly an uninterested and objective assessment of life so far away. My guess is that it was about as reliable as what you'll hear from Republican-fascist sources right now. The same could certainly be said of somewhat closer in location but even farther away in time classical history and biography. When you make such articulations based on such flimsy material as "science" it certainly is more potentially dangerous than if you do the same in the inexact literature of the humanities. I'll forego yet another long critique the use of "history" and "biography" by modern popular-science. I will say when it's a Sagan or Degrasse Tyson who do it on TV, it's pretty much reliably taken as bull shit. Only slightly less when it's a Bertrand Russell or Richard Dawkins doing it.
The modern period in which wars in Europe and the Americas have not been waged on the basis of religious belief have been among the most brutal and murderous in the history of the human species. The First World War, the Second World War, the revolutions in Russia, the wars of conquest waged by the Russian and Soviet Union, the internal warfare that solidified the terror driven, materialistic, officially atheist and opposed to religion Soviet government, the similar and perhaps even more brutal Chinese revolution, the various other Marxist regimes, the fascists in Italy with their invasion of Ethiopia, the biological genocidal regime of the Nazis, the secular United States in the Spanish American war, the various wars to gain territory and extend economic control over Latin America, in the Pacific, the war in Vietnam, the Bush II-Cheney disaster of war in Iraq, etc. and so many others that could be named, all on the basis of some form of the very materialism and rational calculation that Spinoza deified is far better proof than any of the allegedly religious wars that Spinoza had in mind that materialism and rational calculation are, if anything, more deadly than religion. The present Israeli fascist government doesn't strike me as being motivated by the Jewish religion whereas many of the Jewish critics of the conduct of the invasion of Gaza - likely a result of the direct result of the Netanyahu government's corruption, incompetence and irresponsibility and internal political calculation of his government's failure to address a coming attack they were warned of - are motivated by quite worldly and political and financial things.
I will remind you that it was that arch-materialist-atheist true believe in scientism, Sam Harris who called for planning for the nuclear bombing of "tens of millions" of people in Muslim countries as a preventative for the use of the "Islamic bomb" and he was held up as a champion of such materialist-atheist-scientistic "reasoning" with that in the published record. Christopher Hitches was another of the atheist crusaders who their admirers and allies and their basic ideological orientation are never called on to answer for.
The same is true of most of the "religious wars" about which there is much primary historical evidence. Most of those were motivated by economic motives, often the religious explanation secondary or an afterthought to justify what some monarch or the powerful gangster underlings wanted to do. The Crusades were a series of "religious wars" that seem to have been motivated by the situations that feudal gangsters throughout Europe created, as were the "religious wars" that Spinoza would have been referring to. Historically the motivation of "religion" in war is estimated to be less than ten percent. It certainly is true that in the modern period materialism and overt atheism have proven to be even deadlier motives for killing lots of People.
That religion can be used malignantly is no more of a shock than that science, from the start, was thoroughly involved with and mixed up with war making. Galileo and other early scientists were fully involved with things like figuring out the trajectory of cannon balls, later ones on the creation of and improvement of armaments and the theory of war making. I remember when my oldest sister went to university and, looking over the structure of it I was shocked to find out about the existence of "Military Science." They call it that, not "military faith." If that was the beginning of my skeptical, critical view of science and what gets away with calling itself science in universities and academia and the so-called intellectual class, I can't say but that skepticism certainly started when I first looked into psychology textbooks and immediately saw that it was, actually, pseudo-science. I think that effort started with Spinoza's extension of Descarte's method into the realm of human minds and behavior, his ideological assumption that the math and science he, no doubt, was so proud of himself in mastering was applicable to consciousness and other entities that could not be observed or measured was neither scientific nor mathematical, it was sheer ideological assertion made because he liked the idea that math and science, what he abbreviates as "reason" was supreme in its abilities. In that I think he was entirely wrong and the subsequent centuries of constructing the present day manifestations of his assumptions are no more reliable than his original hunch.
Spinoza wrote a lot of stuff, some of it wrong, some of it seemingly plausible, maybe some of it even right, but he wrote lots of stuff. All of it on the basis of his fundamental materialist-atheist-scientistic ideological preference. If he was wrong about that, the chances of most of it being wrong are very high.