If it's truly an unreliable or incorrect source then you should be able to find your argument against what he's saying from his words and not from his person.

If it's truly an unreliable or incorrect source then you should be able to find your argument against what he's saying from his words and not from his person. It's a logical fallacy[0] for a reason. [0]: http://en.wikipedia.org/wiki/Ad_hominem http://en.wikipedia.org/wiki/Ad_hominem