It kinda felt to me, that Damian could of just as easily knocked them out since he literally killed two(possibly three depending how much time passed between them) just about fresh fighting people in a matter of minutes but just took the fastest and easiest thing to do. Safer, but still something like the easy way out. XD

But yeah, it's kinda sickening to know the 'good' guy can be morbid. Probably why it can be felt as worse compared to a killer who is known to be a villain.