Why does this facile and 'truthy' sentiment get reliably upvoted whenever someone posts it? It's neither insightful nor particularly original, and what's worse, it's demonstrably false as a matter of empirical psychology.
"Wants to murder someone" is not a simple, binary, on-or-off property of anyone's mental state, and the man-with-a-mission loading rounds into his gun with cool, icy determination which this argument brings to mind, does not characterize the vast majority of violent crime. In real life, people are subject to psychological influences from myriad sources, and people who are in a state of seriously wanting to kill someone, tend to be in an even more unstable, influenceable state of mind than normal. People's car-buying desisions are demonstrably affected by such minutiae as the physical layout of the showroom, and the order in which the salesperson decides to present them.
What kind of alien to human psychology would you have to be, to imagine that the ready availability of tools to kill someone from far away, without any eye contact or physical proximity, wouldn't make murder psychologically easier to go through with?