It's not an ad hominem. In fact, it's perhaps the most good faith interpretation of your words possible. Ad hominem would be calling you stupid because you obviously know that you have a self and only your own stupidity could explain your inability to see how your self is generalisable. When you go around pretending you genuinely think maybe humans don't have selves, really the only way to take you seriously is to think that maybe you're a p-zombie.

In other words, you don't think it's nice at all.