It's not Bieber himself. It's that I'm not an asshole who thinks if I don't like a particular band/comedian/whatever it means I want to see their performances interrupted and ruin shit for everyone who might be there to actually enjoy it. Never understood why people feel the need to spoil others' fun. Just do your own damn thing.
Besides, I've done a lot of performances before (not concerts, mind) and there's really an unspoken rule: leave the goddamn performers alone to do their thing. The instant you inject yourself into the show, you deserve a brick upside the head.
What about when you have a duo of teeny-boppers playing just before Slipknot at a festival, as in the "Daphne and Celeste" clip that I posted earlier? Those kids had no place being there and deserved every bit of abuse they got - it even says on wiki that they "bullied their manager into getting them a spot at Reading festival" because they wanted to meet Eminem, who was supposed to be playing later that day. Fuck 'em.