If you really have zero sympathy, that displays a lack of respect.
They are trained to fight and stay alive. Most servicemen have never killed anyone and signed up for a job and future job training. The ones who were in the front lines experienced some serious shit. Would seeing your buddy killed have an effect on you? Would you leave that battle field as a 'whole' person? Maybe, maybe not.
It's a "voluntary" job. You are trained to kill people, no what job you go in to learn. This is known before you ever even sign the papers. If you don't want to see your buddies head explode don't join the military.