We needed nuclear arms to teach us that giant bombs that could vaporize cities and irradiate significant portions of the globe were bad? We needed asbestos to teach us to be careful what we used to insulate things? We didn't learn that from the untreated tin cans we stored foodstuffs in that poisoned people in the 1800's?

You phrased this as a "gott'em", but it's really bizarre logic.