Unfortunately, I think most of mankind tends to sort itself into groups of "us" and "them", and we've been doing that since Ancient times. If there's something that some people do, or are, or look like, that's other than what the majority does, they become "them".
I'm sure if we didn't label people by color, or race, or gender, or sexual orientation, or religion, or ethnicity, we'd still be persecuting people who had red hair, or eyes of two different colors, or people who are 7 feet tall.
I'm not sure how to defeat this tendency to sort ourselves into groups, but it does seem to be ingrained in who we are. Just put six little kids into a room together, and they'll eventually gang up on one, for no real reason, other than some real or perceived difference.
Which leads me to this: discrimination is leftover from some past time, when sorting ourselves into us and them meant surviving. It now serves no useful purpose, like wisdom teeth and the appendix.