If you have the time, I suggest reading "They Thought they Were Free," by Milton Meyer. It's a well-known book that tries to answer why generally "good" people joined or supported the Nazi party in pre-WWII Germany.

It's been about a decade since I last read it, but I keep it on my shelf. What I remember, though, is that the reasons why Germans joined or supported the Nazi party vary quite greatly. I remember one passage about a man who basically liked dressing up in Nazi uniforms because he loved pageantry of Nazi rallies. Another was about some Jewish children who saw a Hitler Youth parade in a movie theater newsreel, and really wanted to join.

It's well worth the read if you need to understand why hate groups are so attractive to some people. (Or, to basically "examine your biases" towards people who you have "legitimate disagreement")