The other person in the thread is supporting the same side you support, but isn't making the best points and is, for all intents and purposes, "losing" this informal online debate.
Do you ignore it, jump in, or something else?
The topic, by the way, can be anything... political stance, fandom ship, Harry Potter vs. Twilight, whatever you would like.
Eta Oh, and for more fun, what is that topic likely to be for you?
Don't know, don't care: What's the best way to study for a Spanish quiz?