An Ad Hominem is a type of Logical Fallacy in which someone attempts to assert someone is wrong because of something about who they are. For example: “You have blue eyes, therefore you’re wrong when you say 1+1 = 2” is an ad hominem. “You have blue eyes and you’re wrong when you say 1+1 = 2” is not an ad hominem but a description of the person followed by a rebuttal of their assertion.
Insulting someone during a debate is not an Ad Hominem. Using that Insult as evidence that they are wrong is an Ad Hominem. You are free to Insult someone during a debate; it is not a Logical Fallacy to do so as long as you don’t use the Insult as evidence that they are wrong.