I actually think it has more to do with the notion that you 'should' feel bad about shooting someone, even if it's justified......and if you don't, then it makes many folks feel uncomfortable. I say that without sarcasm, as it's very true that it makes 'normal' folks feel uncomfortable if you're able to shoot someone and not feel devastated by it as they feel they would.
What it boils down to, and I do understand what is going on here, is that 'normal' folks feel......'uncomfortable' around killers and even the idea of intentionally killing someone else.....even if that killer has never killed anyone that he wasn't justified in killing......and that statements of remorse and regret about those killings, even if they were completely justified legally, ethically and morally, make them more palatable to 'normal' folks.
At the end of the day, the kind of callousness some of us take as a matter of course in the face of violence and death, is overwhelming, uncomfortable and a bit intimidating, or at least, very unpalatable to normal decent folks.......and as a result they view us askance.
Know the feeling--It's always the same, that sudden, imperceptible( So THEY think) change that comes over people near you in conversations at parties when they find out you're either :
A) a current or former cop
B) current or former military( federal/reserve/guard/state guard/whatever
C) any form of gun owner
And gods help you if you're more than one (in my case B and C, only recently been more or less made "former" by political crap like the rest of my unit).
Like you're some kinda dangerous animal slipped his cage and got let out amongst them by mistake when they should feel that everyone is a little SAFER because you are there. No one who does not intend to harm others has absolutely ANYTHING to fear from the vast majority of us but on some subconscious level they do. I blame our current media just exactly as much as I do human nature, however.