Ad hominem fallacy revisited

In the past I used to say that insults are not necessarily ad hominems (see ad hominem, no true Scotsman, an arguments from authority) Insults are just insults. They only become ad hominems when they are meant to cast doubt on the other person's position. For example, if I say, "You're an idiot," I may be insulting you, but I'm not committing the ad hominem fallacy. It's only the ad hominem fallacy if I say something like, "You're an idiot; therefore, you are wrong."

I've changed my mind, though. Ad hominem just means "against the man." As long as your comment is against the man rather than against the argument, that's an ad hominem. Since that's exactly what personal insults are, then person insults are ad hominems.

A comment doesn't have to be a mistake in reasoning in order to be a fallacy. Red herrings are also considered fallacies even though they are not mistakes in reasoning. A red herring is a fallacy of distraction. It's meant to draw somebody's attention away from the main point. Insults do the same thing, so insults can be considered red herrings. Ad hominems of this type fall under the general category of red herring. They are fallacies because, like all red herrings, the fallacy lies in the fact that they suffer from irrelevance.