I can't think of any point in Die Hard where John McClane kills prisoners in cold blood (in fact, there are two times where he almost dies because he tries to arrest terrorists instead of just shooting them). And I do consider all such scenes objectionable

Which scenes are you saying are objectionable? The ones where MClane puts the lives of himself and all those he is trying to protect in danger by not shooting terrorists when he should have? Those squick me out. Utter negligence when so many lives are at stake.