Who is "people"?

 If you believe that people need guns to defend themselves against violence, but that psychiatrically disabled people should be banned from having guns, then you believe that psychiatrically disabled people don't deserve to defend ourselves.

If you believe that people need guns to hunt for food, but that psychiatrically disabled people should be banned from having guns, then you believe that psychiatrically disabled people don't deserve to feed ourselves.

If you believe that people need the right to own guns because it's protected by the Constitution, but psychiatrically disabled people should be banned from having guns, then you believe that psychiatrically disabled people don't deserve constitutional rights.

If you believe that banning people from owning guns is a violation of their due process rights, but psychiatrically disabled people should be banned from having guns, then you believe that psychiatrically disabled people don't deserve due process rights.

If you believe that people need guns, but psychiatrically disabled people should be banned from having guns, then you believe that psychiatrically disabled people aren't people.