Gun control is like trying to reduce drunk driving by making it tougher for sober people to own cars.
If we're exchanging common sense slogans, I like quoting Peter Ventoklis: "Taking my gun away because I might shoot someone is like cutting my tongue out just because I might yell, 'FIRE!' in a crowded theatre." (Found in Claire Wolfe's "101 Things to do before the Revolution.")
Also relevant to DC's current gun ban is the Dakota Sioux saying "When you discover you're riding a dead horse, the best strategy is to disout." (Found it in Claire Wolfe's sequil "Don't Shoot the Bastards (Yet).")