I do believe that (while dumb) the gun sanctuaries are not inherently more dangerous.
That being said, the number of armed idiots that have resorted to gun violence despite knowing that other people around them were armed makes me question the "armed society is a polite society". It displays a fundamental misunderstanding of human psychology. Have hammer, will hammer, after all.
I think it is better to say that the lack or prevalance of guns cannot be correlated to the politeness of a society.
I've seen plenty iof polite events be gun free, and I've seen a few bonfire nights in the sticks turn into shootouts.