I'm at the point in my WoW life where I BG mainly for the daily points, whenever I join an obviously stupid/weak/newb team or an AB team where we're down 3:2 resources (longest loss ever), I just don't bother. I afk out and do other shit for 15m, then retry.
I view losing in a BG as a waste of time (I know this entire game is a waste of time, but losing is not having fun while wasting your time). My friend says that I should just man it out through the loss, but I'm one of those people who get irritated with dumbasses doing dumb things and most of the time I opt to just leave the match instead of wasting my energy on them.