Herd immunity

Via Snowflakes in Hell I saw this discussion on correlation between nations with high liberty indices (by a variety of standards) and high rates of private gun ownership.

One point:

The relationship only exists for high-ownership countries. Countries with medium rates of gun density generally scored no better or worse than countries with the lowest levels of per capita gun ownership.

This would seem to me to be explained by the concept of herd immunity. Self-reliance and personal arms are a vaccine against totalitarianism. Firearms are the most effective personal armament invented so far. A small number of people will not stem this tide, but large numbers will never have to confront it, or even be aware of it as a real possibility.