First big problem is obviously that things are only proven given some starting premises, and in this case those premises are highly questionable. Carrying a gun has plenty of costs that might outweigh the benefits.
Obviously it costs money, and peoples' reactions to you may be a cost, but I think the most interesting, and possibly biggest, cost may be the mortal one. Gun accidents are rare but they happen, especially if you're going to be carrying your gun around loaded, so in order to check whether it's worth it to carry a gun, one of the things you might want to estimate is the risk of accidents. Even more interesting to me is the risk that if I become temporarily suicidal, having a gun might increase my probability of suicide, and right now I don't want my future self to commit suicide (unless terminally ill etc.).
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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