When I was little, my older sister liked to torment me. I'd say: "Mom, she's making faces at me!" my mother would just smile serenly and say "ignore her, she'll stop it".
We can all learn something from my mother. When you see absurd remarks here - insults - abject ignorance - inflammatory rhetoric - IGNORE IT. People who post that drivel are looking for attention. They CRAVE attention. That's one end of the spectrum. The other end, of course, are people who are simply brain dead and, as the saying goes "You can't fix stupid"
In either case, the one thing we all have the power to do which simply drives them NUTS is ignoring it. Don't respond. Don't try to "change their minds". No matter what you say, you cannot prove that you aren't "racist". As a libertarian, I have stopped trying to "prove" that I don't want to bring back slavery.
Yesterday I was on an article talking about Voter ID and I pointed out that most states provide a birth certificate to parents when a child is born. The response "Oh yeah? Did you learn that in your Obama "birther" classes?" My reply? "LOL!"
We will NEVER get rid of crude, the rude, the ignorant - because one gets banned there are a hundred ready to take his place. So my advice is this: Ignore them - it will teach them a lesson (or REALLY piss them off)