Well, we all have different taste in music, that's for sure.
Slipknot is interesting, their style is provoking and debatable but some songs are great if you ask me. I believe I had prejudice against them before I actually gave them a chance, starting listening.
I do feel that people in general are much more open minded to different styles of music these days though which I really like. Prejudice, bias, preconception, preconcert, generalizations or whatever you say in english is something I personally dislike myself. It's impossible not doing it sometimes but I strongly try to avoid it, about people, music, well, almost everything in life.