I'm under the impression they're playing it at 110 dB or higher. I can't remember the threshold of pain offhand, but repeated exposure to loud music can cause sustained hearing loss over an extended period of time. If you think it's fine to systematically remove someone's hearing without their consent, you're entitled to your opinion, but it doesn't seem like the sort of thing the United States should be standing for.

Incidentally, there's an editorial in today's Washington Post from George H.W. Bush's presidential physician condemning the torture at Gitmo and elsewhere. (Note that registration is required to read it).