The argument is (and again, it is not mine) that it would have been better to kill everyone currently in the camp, if it meant that the camp was taken out of commission for the future. The holocaust survivor I first heard this from was talking specifically of Auschwitz.
I understand the sentiment, but deliberate bombing a prisoners camp (which btw. also have a number of your own captured soldiers) in order to destroy the facility? In any case a camp could quickly be rebuilt somewhere else, much more complex installations like airplane factories were moved around and continued to operate despite heavy bombing.
