and I'll agree.
Non-monotheistic religions are mostly not strong enough ideologies to use for evil. The statement "I believe in Zeus" is just not serious enough, because it has to be followed with "... and Poseidon, and Athena, and Hercules, and Hermafrodit, and Narciss" - it gets ridiculous.
To be powerful enough for evil, the ideology has to be able to de-humanise a portion of humanity. Before the advent of Christianity, world made do with non-religious ideologies for atrocities. Ellinistic culture and Roman Empire are two that we all know about. I have no idea what Genghis had for ideology, but there must have been some.
The idea of Big Three religions - there is _nothing_ except God, free will is a paradox - introduced a new ideology, plenty powerful enough to be used for evil. I don't know if Hinduism was powerful enough from the beginning or "learned" from the Big Three.
Also, please note that the development of ideologies did not stop on religion. Marxism produced a newer powerful ideology that was used for evil. The basic idea that those who have are all robbers and not quite people is powerful enough. Faschism, OTOH, is not new, just recycled Roman Empire, or Egyptian Empire or whatever else.
The interesting thing about monotheistic religion is that, when applied properly, to its logical extent, it dehumanises entire humanity, not a part of it. In the end, a saint, a sinner and an unbeliever are equal before the infinity of God. That's more than can be said about the other ideologies I saw so far. That makes religion less suited to use for evil, and less responsible for the evils that are commited in its name in my eyes.