No offense on race or nothing, but why are white guys doing this so much?

Hi, everytime I'm online or even with friends I hear all of the same sayings. White guys checking out all women, but when a beautiful black woman pops up with even the right body, a good face, hair and everything MOST of the white guys will say something like "well she would be good but she's black" or I don't like black women butts or boobs. And then my guy friend gets mad at me when guys seem to hit on me, and they go around town saying I'm so hot and I just don't believe it. He says "I don't know what her problem is, tons of guys around here think she's so beautiful and she doesn't even see it". My problem? why I don't believe it? because I'm black. At least 25% but I'm sure that's enough. Why do they do this? and why do they get so offended if I ignore them if "black" girls are supposedly so not attractive?