I would start from entertaining the possibility that your son most likely does not really understand what he is saying. Ask where he learned the word and why he uses it, and what he thinks it means. Odds are, he only has a limited inkling of the power in the word, and uses it because he's heard it from others, and thinks it's cool. He may also enjoy the outrage he gets from adults, but not really connect why it exists, thus mostly finding our offense to be an overreaction.
I've had a lot of success getting my son to stop using such terms simply by explaining to him the common meanings. AS kids are very literal, and once your son realizes that he just suggested a sexual act towards his teacher he most likely will be highly embarassed, and much more careful about repeating swear words he hears on the street. My son now takes no chances, and never repeats a word he's heard without researching it.
When he's older he may use the terms to rebel. But at this age most often its ignorance.
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Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).