And in case you forgot, secularists brought us the most violent conflicts in history, just last century. US slavery didn't need religion, nor did Apartheid. nor climate change or the atomic bomb. Pacifism is pretty much a religious concept, exclusively so until relatively recent human history.
I don't really see how fanatic rationalism has any leg to stand on, really.
They didn't do this 'because of secularism' and that's a big difference. They tried to replace religion with other dogma's en use the religious control for their own purpose. Sure, being a secularist doesn't make you good or non-evil. But without dogmas it will be pretty hard to convince others to blow themselves up for your evil plans.
No one ever committed mass shooting while shouting 'in the name of science', or 'I hate you because I am a securalist.'
People HAVE committed and OFTEN commit mass shootings while shouting "For the Fatherland" or some other nationalist/racist slogan. Last I checked the body count is higher.