I was reading this article about the Swift Vets and Kerry's and the mainstream media's response to them (Link via Instapundit). It got me to thinking about how people go about putting to rest a debate about a factual point and the logical fallacy of ad hominem.
What I came to realize is that while the motives of the accuser might give rise to questions as to the validity of the accusations, looking at the motives alone can not answer those questions. If the accuser can not deliver any evidence backing up the accusation, then yes, the motivations might be elucidating. But if there is evidence, then the motives can not be given more weight. If some Baath Party member were to come forward with a videotape showing President Bush performing unspeakable acts upon a Girl Scout, the mere fact of the Baathist's allegiance does not automatically discredit the tape.
As for the whole Swift Boat story, weight of numbers would not normally be a method of swinging weight for me. However, it was Kerry and Edwards who have been saying that you can gauge Kerry's character by the opinions of those who served with him. Unfortunately for him, he seems to have an extremely limited definition of "served with". Given that his impressiveness does not seem to extend beyond a very small circle around him, I think that those critical of him would have had the separation that virtually everyone who works for the executive branch shall have.