" I can only guess it's because of apathy on the part of non-gun-owners, and an acceptance that guns are somehow 'normal' in your society."

I would say it's the other way around. The sort of libertarian that supports gun ownership in the civilian population is an idealist, not a rationalist. This is an issue science comes across often and it's no coincidence that libertarians also tend to be climate change deniers etc.

Like climate change deniers, the pro-gun lobby are happy to impose their views and their guns on the rest of the population; if your idea of freedom is living in a world where ordinary folk don't carry deadly weapons, then you're fucked, and those with the weapons don't care that they're fucking you; they are increasing the risk of you being shot simply by having a gun and being willing to engage in a gunfight. Collateral damage? Acceptable, it appears.

Evidence is ignored or dismissed; if the evidence is presented to them that they are over 5 times more likely to be shot by simply carrying a gun (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2759797/) they will simply deny it, call it a hoax, suggest the study is flawed without presenting evidence why (in which case they can respond to the study formally - it's free) or start sneering about academics and real life.

What this means is that gun owners are imposing their ideology on others without their consent. The freedoms of these people is utterly irrelevant.