Comment Re:Ad Hominem is called for in this case (Score 1) 413
I would submit, that 'he's not a reliable source', being something that could well be backed up by facts and used as a predictor of probable veracity, would not be an ad hominem arguement, even. And in this case, you could fairly easily back that up with some of the things he's said.
To get into true ad hominem territory, you'd have to get into politcs or percieved intelligence or anything less relevant, really.