Nazis are also born into Naziism. I don't understand your point.
Do you think the average Nazi believed Hitler was a bad man and decided then to follow him? No, he thought, that he is a moral and great man! He thought, that Hitler was great and moral because of his wicked agenda.
The same is with the followers of Mao, Stalin, Pol Pot, Idi Amin and of cause Mohammed.
They stay and become followers of monsters, because they share their point of view and they are convinced, that this believe is moral.
If not they should leave this fleshy, arrogant, cruel, greedy and of cause blasphemic cults.
If they stay, they are our natural enemies and I don't care that they are nice.