Ad hominem is where you aim to refute the argument someone is making by impugning the character of the person making it. Obviously, it doesn't follow that because someone is a bad person, that what they say is wrong.

"Don't believe this guy, he's an asshole" would be an ad hominem argument.

But this is not an ad hominem argument being made here. They are, instead, making the logical claim that, based on the attitudes described, the person comes across as an asshole.

They aren't then saying that that invalidates their arguments - they are taking the author's arguments at their face, and inferring the person's character from them.

Which seems to be a mode of argument you're comfortable with, since you've just done the same to the person you replied to.