Fanatical fear, that’s the motivating force that I’ve witnessed being employed by those that abuse religion to the greatest degree. There are plenty of people engaged in religion that use it to express their love and compassion.
Somewhat contrary to the idea that those who do the greatest evil believe themselves to be doing good, is my observation that they are mainly driven by “the destruction of evil” not by trying to help people or enact a greater good. But instead they have their own personal war on what they perceive as being evil. If one looks at Hitler for example, he did try to “improve” people by promoting “clean living” and enacting “breeding programs”, while himself, well, he was a hypocrite to put it mildly, but he put many, many times more resources into the destruction of the “evil”, those that would compromise what he perceived as “good” as he did trying to “improve the good”.
This does complicate things a bit, but I think that it’s important to make the distinction.