It boils down to will power. History dictates that this arguement is entirely flawed. It would account for some in game behavior, but every person plays like this "because it's just a game". If you were starving and there were a bunch of women and elderly who had food, you would honeslty say that "well in a apocolypse it's plausible" to kill them in cold blood? People who boil this arguement down to such a base level don't understand what it takes to end the life of someone who isn't a direct threat to you. Killing in conflict is sometimes a nessesity to protect and is reactionary. Killing because the lone individual can is a abnormality at best. A sickness. The amount of trauma one would have to endure to regress to such a base instinct is underestimated here.