See, I just assumed that, if he says he's a tank, he knows if he's a tank, and can therefore handle Hammer Station. I just won't make that mistake again.
Truthfully, there's many people out there who are playing this MMO who have never seen an MMO before. If they don't know what they are but are willing to learn, it's worthwhile to teach. If they don't know what they are and all they're going to do is complain about it, ignore them and move on.