You are never going to be able to stop people from using name calling. It's not so bad when they are talking about some one in an article they are reading or some one they see on TV. It's pretty normal to name call and critisize someone who isn't there. Sometimes you are just thinking aloud and talking to yourself when you do it, and sometimes to friends or co-workers. But, it is pretty nasty when they are using it directly in talking to someone, like "You are such a ret*d!". There is no way to stop such nasty behavior. The best thing is to keep your cool and avoid the nasty types as much as possible.
I wish there were a way to stop them, but I know from personal experience that there isn't. School was a really rotten time for me. Adults would tell me to remember that sticks and stones might break my bones, but that names could never hurt me. Yeah, right. What a load of crap that was. Psychological pain hurts, too. I won't even go into the pushing, shoving, throwing things, and occasional hitting, tripping, yanking, and dragging. My parents focus was on getting me "fixed" so that I would be able to fit in. Fitting in is not possible for many of us on the spectrum, and "fixing" is not possible at all. I would have fared better as a home schooled kid, but my parents were into fitting in to the "normal" way of doing things, meaning public school for me and my siblings. If I had kids, they would be home schooled, no matter whether they were on the spectrum or NT.
One thing I have learned over the years through observation, reading, and through news sources. Bad things tend to happen a lot more to bad people than to good people. In large part because they often put themselves into situations that lead to bad outcomes. So, bad people are their own worst enemies, and bring down punishment on themselves eventually.
Just try to ignore the jerks who call you names, and try to avoid them as much as possible. They are not worth your time and energy. And remember, we on the spectrum are all:
A Different Drummer
If a man does not keep pace with his companions,
Perhaps it is because he hears a different drummer.
Let him step to the music which he hears,
However measured or far away.
--Henry David Thoreau