Your son is absolutely right, and that's quite insightful. Clearly, it must be a cultural thing. The Swiss keep lots of guns (in fact, it's part of their "people's militia") yet they don't shoot each other with them.
I grew up in Denmark, and although there are far fewer guns there than in the US, people did have them. But the idea of shooting someone was culturally "unthinkable" at a level that totally does NOT exist in the US. So do we just have less respect for the sanctity of life? And if so, why?