You should report that tank for harassment. Nobody has the right to spout off at you like that. Unfortunately, you'll come across some people who do so anyway. It's unfortunate that you got grouped with jerks on both of your first two dungeons. I've usually found the odds a bit better than that. Yes, joining a good FC should help. But even when in an FC, you may still end up in DF runs occasionally, either for Roulette or when not enough people from your FC are available to run an instance with you. You shouldn't have to put up with insults just because you're grouped with strangers.