To follow on (possibly tangentially :)) from sanguinity's point: those girls are wrong to say they're bisexual. But they are a tiny minority compared to all the actual bisexuals in the world, so anyone who acts like they're representative is an idiot. And in the end it's those idiots who do more harm, by being prats to real bisexual women.

(men who enjoy watching fake bisexuals but realise they're fake are, imo, not so much an issue, though it might be nice if they said "Hey, you don't have to pretend to be bi for you making out to be hot")