I think that the fact that pilots are already trained for extreme situations they would be equipped to handle a gun.
There are also mandatory psychological tests that are taken by the pilots in the gun program.
I have to ask why you think they couldn't handle a gun....but on the other hand, "idiot" pilots could handle "less than lethal weaponry"
Info from a pilot friend of mine: he speaks of sub-sonic rounds that don't exit the initial target.
Also, a bullet hole would not cause a decompression of the aircraft. The pressurization control valve is going to adjust to keep the pressure stabilized.
The fact of the matter, all this is moot.
We are just pawns, and are subjected to, and must comply with, whatever laws are passed, We just have to pay for them.