My reasoning for it is this. I like guns, others like guns, and so it makes us happy to either have guns, or at the very least have the option open to us to have guns. Yes, guns kill people (it really is people that kill people, but like you said, guns greatly facilitate the process), but lots of things kill people. Cars kill people, gas leaks kill people, toppling trees and hundreds of other things. There's no way to protect everyone from everything, or even to protect a single person from everything. If all guns magically vanished, then that guy in Colorado would have planted a bomb and set that off instead. He clearly had the ability considering what was in his apartment. I don't know the statistics, so I don't know whether and in what way gun restrictions would impact crime. I can see it going either way, but the majority of me (the cynical, and therefore realistic part) thinks that if it does any good, it would be a very insubstantial amount. So the question is, do we want to anger and upset millions of people, to preserve maybe a handful of lives a year?

And perhaps it makes me callous or evil to say so, but for me the answer is no. More people than that will die from choking on random bits of food, or a multitude of other things that are as much outside the control of the victim as being shot by a psychopath.

That said, I have no problem with some sorts of background checks. For instance, if the person has been accused and convicted of violent crime, or something along those lines. And a mandatory course on gun maintenance, safety, and shooting, for all buyers would be a good idea. Nothing too strenuous, we're not training people to re-enact Call of Duty in real life, but enough for them not to shoot themselves or others accidentally, or confuse the safety with the trigger. After all, we require people to get driver's licenses, so some sort of gun training program doesn't seem like a ridiculous or even difficult to implement idea.