I agree with Ken Howell. In most times and in most cultures, killing another person was a relatively rare event, and those who did so generally had what Massad Ayoob calls "The Mark of Cain" on them. That is, they were regarded by others in the society with some fear and suspicion and set apart from most of their fellow men. This leaves aside war, of course, where soldiers were "given permission" to take another man's life, or self-defense.

It is certainly fair to say that punishments were harsher in the past than they are today, particularly for lesser crimes. However, as a rule, when those punishments were applied, it was on the basis of society judging and passing sentence, via some sort of legal system, rather than an individual being "judge, jury and executioner." I think in the past, as today, that is considered an exceptional event, and a person who performs such a thing, particularly repeatedly, as apparently Col. Askins did, would also stand outside the norm, in any time or place. I believe that is what Mr. Howell meant. I'm sure that he'll be along to correct me if I'm mis-stating his position.