Are straight people allowed to say "faggot"? Are white people allowed to say "nigger"? Generally no. Our unwritten speech codes require that those words be used only by gays and blacks, respectively (black gays can say both). Which is just as it should be: minorities can reappropriate slurs if it empowers them or even if it just humors them — I think it's funny when fellow gays sarcastically say "Hey faggot" to me. But it wouldn't be so funny if, say, my heterosexual boss said it.
Sorry, straight people: you don't get to say "faggot." (I can still be fired for being gay in most U.S. states, so you still have the better end of the bargain.)
Coulter is heterosexual, so I suppose I should condemn her as well. But note that she was using the word "faggot" with virtual quote marks around it. Surely all of us are allowed to do that — just the way I used the N word in quote marks above. She didn't say "John Edwards is a faggot." She would never say that — not because she respects the rights of gays to full equality before the law (she doesn't) — but because it wouldn't be funny. Coulter wants to make people laugh more than anything; she is, as I have argued here, a right-wing ironist and comedienne as much as she is a political commentator.
More on why Ann Coulter is little more than a purveyor of unfunny political slapstick in is TIME magazine