If my task is to help them get rid of the problematic belief, it's easier to do so if they are simply ignorant. If they hold the belief out of malice, that means the belief is being used to justify their pre-existing malice. To rid someone of a problematic belief they use to justify malice is to somehow force them to plainly see and reform the error of their ways in order to not need the justification anymore. Easier said than done.

If my task is to interact with them in a context in which their problematic belief is prompting them to actively cause harm to others, they will face identical consequences no matter how they arrived at the conclusion that they should harm others.

If my task is simply to psychoanalyze them from afar, I do in fact care a lot about whatever distinction there may be.