Everyone always believes they are doing the right thing.
Even as they murder, kidnap, govern, rape, steal, and trespass- as they archate.
If they truly believed they were doing wrong, they would stop. You aren’t going to convince them that what they want to do is wrong, except in exceptional cases. They have excuses and justifications for what they want to do handy and rehearsed.
So… what to do about it? (Short of killing them all, I mean.)
The best strategy I’ve found is to live by the Zero Aggression Principle. You may have other ideas.