Gun free zones are free killing zones. Every mass shooting I can recall, except one, happened in a gun free zone. [...] When armed good people are present someone might still get killed but it's also quite certain the murderer will be among the people shot.
The problem with non-uniformed civilians carrying guns is that they cameoflage the bad guys. If you see a person carrying a gun in a place where nobody routinely carries a gun, you call the police because something is wrong. But if lots of people carry guns all the time, you end up either raising a lot of false alarms, or risk allowing a shooter to get to his victims and start shooting before anyone knows to stop him.
IMO if we're going to have people around carrying guns to keep the public safe, those people should be professionally trained and in uniform. That minimizes the "is that armed guy a good guy or a bad guy?" problem.
Lucky for us, the bad guys are happy to follow the requirement that they walk around brandishing their gun so that we know they're one of the bad guys.
Really, there are two problems here. First, an unequal balance of power. Bad guys can and will get guns. "Good guys without guns" sounds a lot like "victims". Second, lack of police coverage. If police were everywhere, I would be more inclined to say that civilians have no need for guns (except to protect against the police, but that's a philosophical issue), but I'm not interested in paying the taxes to support that.
Also, it's not like there couldn't be a training requirement to have a permit to carry a weapon, as opposed to owning one. Given your sig, you're from Canada. We already have possession permits. Do you really think it's so difficult to have a higher standard for a concealed carry permit? Many places in the states (perhaps all that allow concealed carry) have a licensing requirement, which appears to have a training component.