bigotry sucks
I can only explain it by saying that people fear what they don't know. These thoughts are historically rooted in the idea that the "wild black man is going to go after your white women," which goes back to the reconstruction and early 1900s lynchings. The media perpetuates the fear. Watch the news tonight and count how many times they try to scare you. For example, I heard this two weeks ago "Jetliner escapes runway and kills an 8 year old boy, can it happen here?"
Another reason this continues is because many of us do not say anything when we hear our neighbors, aquaintances and family members utter racial comments. I am ashamed to say I am guilty of this at times. It depends on the company I'm in. When I worked in a grocery store, some really good friends of mine (interracial couple) came in with their 2 babies. They were in the next line behind my checkstand. The 60ish white man in my line was so upset, and spent so much time staring at them, it took him a good 4-5 minutes to write his check. I had to keep asking him if there was a problem (knowing what the problem was). He didn't even answer me. I was angry, but of course, being at work, I was not in a postition to say anything to this a$$. In most cases, I try to make it clear that I don't appreciate or agree with the comments people make.
Silence = Acceptance
Sorry you (and any other Americans) have to go through this.