As the author himself notes, he was also "mugged" by reality. However, the key takeaway is his new-found comprehension of the following essential truth:
Gun-free zones aren’t the answer, and other gun laws are not working. Most gun control measures tend to disarm law-abiding citizens rather than criminals, who do not obey gun laws.
It should not take a threat of bodily harm for liberals to come to such an understanding, but it seems as though nothing else quite reaches their closed minds like being exposed to armed members of the criminal class in person, alone, and unprotected.