That's like saying "Spitzer only became a story because Spitzer became a story." It's an inartful dodge of the sort to which one must resort when one sets out to prove that the sky is red.

Prostitution is sexy. It gives a story legs. See, for instance, Craig Vitter. If one doesn't have ideological blinders on, one will see that when big-shot politicians get connected to call girls, it's news, but when they get caught up in vanilla affairs, it's not.

If one, however, believes that the media is biased against one's favorite party (and does anyone, anywhere, believe the opposite?) then this perfectly simple (and accurate) explanation isn't good enough. Vitter, rather, was big news not because he was linked to a prostitute but because he's a Republican. And Spitzer was big news not because he was linked to a prostitute but because he's...er, because he...got caught? I guess?