Because racism is learned. It’s the same tired tropes they heard from their parents. Today’s racists are racist against Central American and Caribbean immigrants. Twenty years ago it was the Middle East. In the 1970s it was southeast Asians. Before that were… everybody else. This is America. There’s always some new cultural group to demonize.
I came to reddit from fark, before the digg migration or exodus or whatnot. There was also stumbleupon, and the others are all lost to me.