But this graph points out that violent crime is decreasing the in the US over roughly the same period of time described above:
This suggests that there is less reason for people to justify using protection as a reason to own a gun since there is less likelyhood that one will be affected by violent crime. Of course this doesn't mean that violent crime doesn't happen and one might reasonably choose therefore to own a gun for protection, but the trend lines do not jive. Fewer violent crimes suggest that protection should be less a factor used to justify gun ownership.
But this assumes that people are basing their decisions about why to own a gun based on unvarnished facts. Something is likely convincing people that violent crime is a bigger problem than it really is. There may be certain groups that are advantaged by convincing people that crime is more prevalent than it actuall is. It is also commonly pointed out that local news tends to hype local crime since it tends to attract viewers. I'll surf around and look for attitudes about the prevalence of crime and see if it conflicts with actual crime rates, but this might lend support to the argument below that the information we receive about factual matters is distorted.
In fact it might be worth investigating who or what best determines attitudes about crime.
