I actually know a couple, and I don't really mind them. Hell, I think a lot of the art is pretty good.
What I think is that people feel that it is different, and humans really take anything they view as different as a bad thing, so it just leads to hate. Though, I do not agree with the ones who make (or forget in) animal suits, or rather, 'fursuits'. That stuff's just weird, in my opinion.