You are google jockey and didn't properly conclude what qualifies as ad hominem.
"You are stupid, therefore you don't know what ad hominem is." That is an example of ad hominem, premise A, ad hominem, concludes B. Simply calling you stupid isn't ad hominem, it's just insulting!
...I'll just quote someone else instead:
"It is not a logical fallacy to attack someone; the fallacy comes from assuming that a personal attack is also necessarily an attack on that person's arguments.
Therefore, if you can't demonstrate that your opponent is trying to counter your argument by attacking you, you can't demonstrate that he is resorting to ad hominem. If your opponent's sarcasm is not an attempt to counter your argument, but merely an attempt to insult you (or amuse the bystanders), then it is not part of an ad hominem argument."