What's the difference? In either case the people in question are incapable of advocating their own rights.
If you have doubts just spend some time downtown on the streets of any major city. Should these people have a right to carry firearms?
I have to wonder what insane people are doing wandering the streets.
Anyone who lacks sufficient mental capacity to advocate their own rights, or who is incapable of appreciating the consequences of their actions, should not be permitted to have a weapon of any kind let alone a gun. Anyone who gives an insane person a weapon should be charged with a crime.