Your analogy doesn't work. You'd need to be chopping the machine-gunners hands off, rather than taking away his gun - we're talking about removing a part of someone, something he was born with, and didn't ask for, to preventing him doing harm.

Which isn't to say I wouldn't do it if I thought it'd be the best thing to do, but this is why we're talking about it - to work out what the best thing is...