If you are in a "debate" with someone and they start name calling it
becomes very tough to convince anyone of anything. This particular
situation comes up alot if you are in some kind of Internet chat room/forum.
As with everything else, you have to make them not want to insult you.
Make them feel silly for resorting to the name-calling and they will police
themselves. And even if it doesn't stop them, it makes anyone else
listening/reading think less of them and their ranting.
You may want to go easy on the personal insults/namecalling because people
might think you don't have anything intelligent to say