Welcome to the forums. I see you've already seen the common forum attitude: "Someone being a jerk? Stoop below their lvl and be a bigger douchebag! Nobody will outdouchebag me!"

If the run is moving along fine and someone is just being rude for the sake of it, ignore them. Most of the time they're just doing it to get a response anyway. Take a deep breath and move along. They usually get bored if nobody responds and the odds are highly unlikely that you'll ever see the guy again.