Then keep the loonies locked up. It is unreasonable to think that mere laws will keep guns out of the hands of all the dangerous people walking the streets today - indeed, locking them up doens't assure success since the Texas Seven stole the guard's guns and were armed even before setting foot on non-prison soil.
But don't create a caste system in which some people are denied the legal ability to buy guns that others of us may do - such that we all have to go around proving that we are members of the latter class, not the former. For one, it's offensive to have to demonstrate the class one is in, or even to have classes at all, and second, it's not like the background checks are able to reduce criminal access to guns at all in the first place.
Amen. The idea that someone is too evil/crazy to be armed, but not so bad that he can't be held, strikes me as totally foolish.
Our goal should be a 100% armed society, one where there is no longer a gun gap between whites and blacks.