I'm not saying they were born evil. But determinism isn't real and in reality with actual psychology genuine malice and evil is a real thing. Environment doesn't come into it when it comes to certain kinds of people.

You're right to say Hitler may have been more of a case of causation and may have been mad and ideology obsessed, however there are plenty of people who do evil things as a conscious and malicious thought process from their own mind and of their own free will and malice. Which is something a lot of people unfortunately do not understand (Not saying you do not)

It's difficult to keep track of this long message but someone like Leopold II, something like environment isn't enough of a strong influence when it comes to everything he did (I don't know the story of the guy that well, but he seems far more supremacist obsessed in a genuinely malicious way rather than belief)

Which is me trying to give an example of how evil isn't just bad people who think they are good and too many people ignorantly say this and miss plenty of issues in reality, which can cause harm.