What I find sanctimonious is the automatic grouping of anyone who kills for whatever reason as "bad guy". I would not put a soldier and psychopath in the same category, nor would I judge a person who killed to protect innocents and a person who killed innocents the same. There is a difference between killing a man in cold blood and putting down a rabid dog.
Reasons and context matter to me in judging the actual deed. That's where the line between villain and anti-hero lies. Do you kill for your own gain or for the perceived good of other people?
Also, as somebody pointed out, the notion that killing is the ultimate worst you can do to a person is purely subjective. I'm sure there are people who would prefer death to living crippled, catatonic or haunted.