I would posit that we need guns for the same reason we need fire extinguishers and seat belts. None of them lack for purpose soley the cause of human shortcomings.
Firearms aren't just about self defense. I take great pleasure in using mine to put meat on the table, or just for the sport of it.
Were I the last man on earth, I would still need guns. It's not an obsession, it's a way of life.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)