I don't think that it is a question that the people here advocate enjoying killing, as I don't relish the prospect of killing someone. People that do are sociopaths. The fact remains that there has to be someone (i.e soldiers, police) that are WILLING to kill people, if the people of Canada (through their elected representatives) dictate that there are people who require that level of violence to be inflicted on them to get them to stop what it is that they are doing that we find so abhorrent (genocide, mass rapes, terrorism, etc). If one is to join the military, they are expected (unless they are a padre) to be capable of having to be capable of killing someone. Unless I missed the memo, that's pretty much all there is to it. If you are a clerk, a cook, a bosun, a aircraft navigator, if push comes to shove, you best be ready to kill. If not, get out of the military (or don't bother joining).
Does one need to be a raving lunatic in peacetime, challenging all comers to a to-the-death round of fisticuffs? No. I'm sure that some of the most effective soldiers, sailors and airmen during all the wars ever fought were quiet, reflective people who didn't care much for killing, but were able to justify to themselves, at least, that that is what was required of them (at that particular moment in time). I'm more of a fan (in film anyway) of the idea of the reluctant killer, who only kills because they have no other choice, rather than the Rambo-style "kill 'em all, let God sort 'em out" mentality.
As mentioned in an earlier post, a good read is "On Killing" by Lt Col Dave Grossman. Very interesting look at how historically soldiers have been averse to killing, and it is only in modern times that militaries have become effective at creating "killing machines" (my quote, not his). His point is that we require controlled killers (police, military) not out of control killers (kids who watch too much violent media (movies, video games, etc)). Again, it is all about control and discipline.
Al