Well put, by a poster with expertise on the issue.
The Petit deaths were a tragedy. Sometimes bad things happen to good people and there's no reason, and there would've been no mitigation. The two ex-cons who randomly selected and targeted the Petits were not going to be dissuaded; they wanted to rape and kill, period. The petite wife with two young daughters probably would not have survived even had she been holding a gun in her hand when they walked up (they were bigger, faster, stronger, there were two of them, they weren't disadvantaged by surprise, and they would've had no hesitation to kill her had she fought back. That much, we know.)
Sometimes bad things happen to good people and there's no reason. This can be really, really hard for strident conservatives to accept. There always has to be a REASON, a BECAUSE, because otherwise the world doesn't make sense and it can't be controlled, and control is everything. The Petits died BECAUSE she didn't have a gun. The economy collapsed BECAUSE rich conspiring bankers got greedy. Health care reform is a bad idea BECAUSE poor people are stupid and they don't buy insurance and they deserve to suffer. Abortion should be outlawed BECAUSE little sluts who sleep around deserve to be punished, and God wants women to have anacephalic babies who are born without brains to linger in agony for days before certain death. There always needs to be a BECAUSE, something to point to, something that can be controlled. The problem is ... life doesn't work that way.
With respect to guns, personally I find it a huge tragedy when kids accidentally slaughter themselves with guns they find in their parents' nightstand drawers.