I've heard the argument in the title of this post........well.......not as much after the Arizona shooting as after other shootings. Probably because it happened in one of the states with the least restrictions on carrying firearms. And look what good that did.
But I'm sure I'll hear the argument again when a guy shoots people in a state other than Arizona. The whole concept of if people were freer to carry guns then there would be less incidents like this is flawed because most of these mass shooters don't seem to care if they die or not. Of course the follow up statement is that "yeah but they would kill a lot less". That might be true if suddenly every person carrying weapon is trained enough to hit their target in such a high stress situation. And let's face it, most gun training classes don't train you for that crap.
Also, what if there were multiple, everyday people armed and ready to try to stop the shooter from various sides? Boy would I love to be caught in the middle of that mess.
My point in all this is that if you are an unreserved supporter of the rights of citizens to bear almost anything, just be honest and say so. Say "I like guns and I believe the founding fathers wanted us to have the right to bear arms to this degree". Don't pull the altruistic, public safety argument. Because it's a losing one for your side. Our murder rate in this country versus the rest of the civilized world (who don't have gun laws near as free as ours) is ultra high. And the fact that people don't have enough guns isn't the reason.