Why are Pope Benedict's comments on condom use controversial?

MoJ readers are probably aware of the controversy arising from published comments by Pope Benedict characterizing condom use by male prostitutes as a step toward moral responsibility to the extent that it reduces the risk of disease.  (I won't even purport to offer a direct quotation, as there appears to be some dispute over the proper English translation.)  To the extent that observers leap to read into this comment an endorsement of condoms in general, I can see why the comment would be construed as controversial.  But if Pope Benedict indeed was limiting his statement to male prostitutes, who overwhelmingly serve male clients, what would be the argument against condom use?  If there is no contraceptive function to the practice, why would the comment be remotely controversial?  A New York Times article quotes experts pointing to the different weight that various Church statements carry, as does George Weigel, who offers this argument, among others, in responding to the controversy:

The second false assumption beneath the condom story is that all papal statements of whatever sort are equal, such that an interview is an exercise of the papal teaching magisterium. That wasn’t true of John Paul II’s international bestseller, Crossing the Threshold of Hope, in which the late pope replied to questions posed by Italian journalist Vittorio Messori. It wasn’t true of the first volume of Benedict XVI’s Jesus of Nazareth, in which the pope made clear at the outset that he was speaking personally as a theologian and biblical scholar, not as the authoritative teacher of the Church. And it isn’t true of Light of the World. Reporters who insist on parsing every papal utterance as if each were equally authoritative — and who often do so in pursuit of a gotcha moment — do no good service to their readers.

Why do we even have to go this far?  Why can't the Church just say that it is better for a male prostitute to use a condom than for a male prostitute not to use a condom?  (For the present inquiry, I'm putting to the side the question whether the doctrine of double effect would justify condom use to prevent the spread of disease in other situations.)