Penn and Teller put it pretty well in their first episode of Bullshit. To call someone a moron or an idiot is slander and you're open to lawsuits. To call someone an asshole or a motherf***er is expressing an opinion, and you're pretty much in the clear.
Take it a step further and you're getting into the slander/libel territory. A 14yo brat calling someone a "faggot" I would argue could get into lawsuit territory. If the target was in a position that, should the accusation be true or generally perceived as true, could cause irrepairable harm to that persons livelihood. Teachers, for example, may have a cause to start a lawsuit since along with the label "faggot" (homosexual) is an implied "pedophile".
With regard to this whole "movement", I liken it to Westboro Baptist. They are an incredibly vocal minority looking to stir up crap. They are within their rights to speak their opinion wherever and however they wish, so long as it is not destructive to others. They can picket all they want, but as soon as a rock is thrown through a windshield, they are in the wrong.