Good writeup on why the Washington Post allows anonymous comments. The big takeaway is:
"Man is least in himself when he talks in his own person. Give him a mask, and he will tell you the truth."
In other words, without anonymous comments, people are more reserved, trying to put their best face forward so to speak. Are there horrible, racist, and disgusting comments made? Of course. But there are also good, mature, well thought comments that for the most part counteract the filth.