You make no distinction between legalisms and American principles. I think most observers agree that the legal rights of the detainees are murky. This has nothing to do with American principles, however -- unless your view of American principles is that of exploiting loopholes because the end justifies any means.
What American principles say "be nice to terrorists"?
Do you have any examples of these previously unknown American principles in action in the last 227 years of our history?
What did the US do to partisans and terrorists in the Philipines? How about in Vietnam?
Terrorists and unrecognized illegal combatants neither deserve nor should exepct any quarter from US regular forces.