Witty comebacks to immature insults?

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Most of us have been there, some immature person throwing silly insults at you that don't hurt you at all, but are annoying to constantly listen to. I found myself in such a situation today. A guy in my class started throwing insults such as "homosexual" at me, apparently believing that someone's sexuality is something to insult someone over. Just to note, I am not homosexual, so he was also making a false statement. I stayed calm during the entire verbal attack, saying things such as "Do you really think sexuality is something to insult someone over", and "Verbal attacks aren't very hurtful", but of course he didn't listen to me and kept the machine gun of immature insults rolling. So, mylot, have you ever been in such a situation, how did you react and do you know any good, witty comebacks?