[nkohari]

To be fair, he said he was "railing like a zealot" -- a subtle but important difference. Calling someone a zealot is attacking them as a person, calling their behavior "zealot-like" is only attacking the behavior.

[ahoyhere]

Ah, yes, one word changes characterizations like "railing" and "zealot" into… a slightly (slightly) subtler ad hominem. But still an ad hominem.