Even if they are criminally insane?!
Look, I agree that we need to lock criminals away and take the mentally ill off the streets. The reality is that is not going to happen due to the cost and practicality.
Therefore, keeping illegal aliens, criminals and the mentally dangerous from purchasing firearms is prudent.
Are we engaging in hyperbole?
Most of the people affected by this are not insane at all; mostly temporary stress overload; it's usually over when they get their physical health back on line. We can't afford to harm the security of this country, and the rights of hundreds of thousands of individuals, for a very few kooks. Arm the public in all places, and the kook problem goes away.