The other night, I was accused of attempting end a debate with ad hominems. We will leave aside the fact that my correspondent used an adjective as a noun. Let's take the rule against that as read.
Argumentum ad hominem means argument against the person. Very roughly, it's Latin for playing the man and not the ball.
If you freely admit that you are mocking me and say that I am not open to rational discussion, that's ad hominem.
If I respond to your mockery, non-sequiturs and general attitude of entitlement by finally telling you to fuck off, that's not ad hominem, that's simply what I should have done two hours earlier when I thought I would be having a discussion about ideas.
Here's another clue for you all:When I say "with respect," I mean it.
When I say "with all due respect," it's a euphemism.
Use this trick wisely.