Perhaps the Pentegon doesn't know about this site. What is the website do you know? Could these pictures had been posted by someone other that a soldier, using this for propagada purposes? How can one prove that American forces took or posted these pictures?
It's call NowThatsF***dUp.com without the asterisks. The site is heavily oriented towards the military and the people who run it are obviously familiar--they might even be in the service themselves. The vibe is pro-America, pro-war and not leftist by any means.
I will not post a link to the site, but you can Google "soldiers trade photos porn" and find links to sites which have links to this obscene site.
I caution you, however, that the site doing this is a very, very nasty site. It doesn't seem to have any malware stuff on it, but it is a very ugly site, indeed.
Visit at your own risk.