I'm still learning the trade myself, so I won't try to offer you advice on the mechanics of tanking, but I'll say that if people get attitudes and leave look at it as a positive. You don't have to put up with their crap anymore, and they're really just hurting themselves. It's like a kid who refuses to eat because he didn't get his way. It's not mom and dad who are going to be hungry later, just like you're not the one who's going to be stuck in a lengthy lockout or queue. What they've done is a reflection on their own personality flaws, not your tanking skill.