There are people who say that name-calling is not an ad hominem unless is it explicitly claims causal connection between one's character and one's argument, with words like "because" (eg "you're wrong BECAUSE you're an idiot"). Here is one such view:
But forum posts are not mathematical proofs, and nobody explicitly shows causal connection when it can be inferred from the context. When you read a disagreeing reply, it's reasonable to assume that what you are reading is a counter-argument (as opposed to, say, an attempt to make someone cry), and so everything in it should be treated as a premise of that counter-argument.
http://tinyurl.com/2fg8fu
But forum posts are not mathematical proofs, and nobody explicitly shows causal connection when it can be inferred from the context. When you read a disagreeing reply, it's reasonable to assume that what you are reading is a counter-argument (as opposed to, say, an attempt to make someone cry), and so everything in it should be treated as a premise of that counter-argument.