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Attacking someone's work is not ad Hominem. If he called him an asshole or some other unrelated insult that would be ad Hominem.

If just listing the guys work comes off as insulting, you gotta wonder...

By attacking his previous work, you don't address the question at hand, and sidetrack the debate on the worth of the messenger.

Strictly speaking, you could say it's an ad opus attack, which is still fallacious.