Tana French (Dublin Murder Squad series) writes novels about flawed people. Very flawed people. But her advice to writers about how to approach those characters is simple, clear, and for some likely very difficult to follow:

Your character is always right. No real person thinks they’re being stupid or misguided or bigoted or evil or just plain wrong – so your characters can’t, either. If you’re writing a scene for a character with whom you disagree in every way, you still need to show how that character is absolutely justified in his or her own mind, or the scene will come across as being about the author’s views rather than about the character’s. You can’t make the judgement that your character is wrong; let the readers do that for themselves…

Trusting the character, right or wrong, is another way of trusting the reader.