I dont even know how to start. Whites hate Blacks. Christians hate Atheists. Straights hate Gays. Feminists ask for equal rights without even thinking if it is still equal. The Christians want to burn every homo because God made man for woman and woman for man. Whites perceive all black people as good-for-nothing thieves. Why?

1. Discrimination exist because people are educated differently, differences, fear of the unknown and a lot more factors.
2. Many of the examples you stated are incorrect and may offend people, so I'd like to adress them
-White hate blacks ~A loooong time ago, but very few do now, yes we still do have a few people, but do we see people burning on crosses and not hear it on the news? Not at all
-Christians hate Atheists ~ Sure, I don't hate them, but there's bound to be some conflict between opposing view pts, but not always HATE. Hate's a strong word. i have plenty of Atheist friends but that doesn't mean i agree with them.
-Feminists ~Women's rights are NOT equal, much to many people's surprise. Popular culture just makes us think so.
- Christians burning homo's ~ I'm Christian, and i don't burn homo's. Don't generalize. i may disagree with gay marriage, but i plan on arguing with words, not idiotic actions like persecution or threats.

You have just thrown so many stereotypes around it's unreal.
Discrimination happens for many reasons. People are generally scared of what they don't know, so they fight against it. But I would say the biggest reason for discrimination is stereotyping like you have just done there.
Not all whites hate blacks, and in fact racism can work the other way around. it's just not as media covered.
I'm a gay athiest and I have straight and Christian friends so no, I'm sure they wont burn me for being 'homo' as you so gracefully put it.

Thank you,
truthfully stereotyping like you( I'm a vegetable) is one of the main reason discrimination exists. I understand that wasn't your intention, but please be careful with what you say

You are laying a blanket over each group there pal, not every person feels the same way as others. Sure there are some people who have hate but there are a lot of people who do not, I think everyone can be accepting of everyone else.

Most people don't like what others believe in mostly because they they think their way is the only right way. That's probably why so many people hate the other people who aren't like them. My opinion would be to respect someone elses decision.