Why people are still prejudice even if they don't think so?

Kanye West. So he totally runs on stage, ruins Taylor Swifts moment and is a douche yes. But why, do I have to hear something like "...he represents black men in America"

Ok, so please explain to me what Kanye West being a douche has to do with Black Men in america. When a white person does something no one's like "see white men" Nope, but a black person does something and they represent everyone of that color. It's bullshit and it annoys me. My mind didn't even think about the rest of the black men, because everyone is different.