As I mentioned earlier, the purpose of the nonuniformed combatant rule was to discourage "unlawful warfare" and confine the fighting to the battlefield. The Arab world, on the other hand, recognizes that they can't engage us conventionally. Therefore, they use "nonaffiliated terrorist organizations" to do their fighting. Prisoners taken in such activities should be dealt with harshly... to deter others who would follow suit. In the long run, it is far more humane than allowing such a cancer to fester in civilization.
And do you really think that “moral and religious codes” (at least the ones you and I might subscribe to) condone killing a caged human being at will?