I think you are missing our point. Whatever the reptile does with its prey is nature. However, if I decide to rip up a rat into little pieces myself while it was alive, would that be ok with you?
This is part of the reason that reptile keepers have a bad reputation amongst non-reptile keepers. One of the misconceptions is that we enjoy watching little fuzzy creatures suffer. I don't care if a keeper feeds live or F/T. All I expect is that the prey animal not suffer unnecessarily.