"Traditional religious ideologies" kept slavery legal, women repressed, sexuality repressed, and things like freedom of religion, a very cherished right of ours, is explicitly prohibited in Judaism, Christianity, and Islam. If we stuck to these religious ideologies, Salem may not have been one of the last major witch hunts. Women who aren't virgins on their wedding night would still be degraded. And don't forget these traditional values did help spawn the Klan. Hitler, Stalin, Mao, they weren't drawing from Enlightenment values, but rather they tended not to agree with or like such things.
Religious ideologies, just like non-religious ideologies are a very mixed bag. You can find Christian arguments against slavery and for freedom of religion from the 2nd/3rd C or so. Your interpretation of the text is not universal.
Anyway, I'm not arguing that religion is wonderful, cute and fluffy because it wasn't, just that people overstate its role in causing violence as they don't compare it equally with the totality of non-religious ideologies.
Marxism and its antecedents were unequivocally a product of the Enlightenment, continuing the trends of the more radical factions of the French revolution. It really wasn't about 'tradition values', which were seen as the primary obstacle to humanity reaching a true freedom.
Modern Humanists like to whitewash the Enlightenment as being about their values, but that was only half of the Enlightenment. The other half was often decidedly illiberal.
Nazism/Fascism were more from the Romantic tradition which was often a response to the Enlightenment, however the Social Darwinism and Eugenics components were clearly products of the Enlightenment.
No need for hagiography of the Enlightenment, major social and intellectual changes branch off in countless different ways not all of which are 'good'.
No, Darwin did not "buy into those things" (it is improper to call such a theory) but rather to the contrary wrote the opposite of social animals developing a conscience to drive cooperation and group adhesion, enhancing the survivability of both the group and individual.
The two are not mutually exclusive.
Darwin believed it inevitable that the 'lesser races' would become extinct. He also viewed women as inferior to men in their capabilities.
The 'social' in social Darwinism is really redundant as he never believed humans were somehow exempt from such forces of nature.
This is not to say he was malicious in his intent, just that is what he believed was scientifically correct.
No need to whitewash him just because he is an important figure to many. He was a man of his time, and scientific beliefs don't have to conform to modern liberal values.