Why don't we require by law that all law abiding citizens wear a T-shirt that says, "I'M A LAW ABIDING CITIZEN SO I AM TOTALLY UNARMED?" Before you laugh at that, just think, such a law would create jobs (for T-shirt manufacturers and material suppliers), would generate government revenue (ie, our taxes will go up), and magically make those who otherwise would be criminals to stop their evil ways and join everyone else in wearing the T-shirt.
Kum ba yah, my lord, Kum ba yah! ....