You don't need to explain anything to me. The government cannot punish speech unless it incites "imminent lawless action." Determining what speech meets such standards is based on a consensus and certain people will certainly object to the conclusions reached by such consensus. The same applies to determining what mental states meet the standards of someone being an imminent threat if they were able to own a gun.
Obviously I do need to explain it because limits are not specifically about "immenent lawless action" in limiting free speech. There are very specific tests for protection such as SLAPP value, defamation, invasion of privacy, provocation to anger and "fighting words", and words that create a "clear and present danger" or "immenent threat". The common thread in all of this is that the words themselves are protected, however usage of with ill intent is not. For instance, yelling fire in a crowded theater when there is no danger can cause a panic and endangers the rights of those in proximity, yelling fire in a crowded theater that is on fire is perfectly legal. Same thing with firearms, a person who is not going to commit a crime is not a danger with a 10, 20, or 100 round magazine. The psych test is not enough, all it would take to infringe would be a psychologist who wants to end gun ownership finding for the state or.....as is the case with most gun laws an over broad definition of psychological disqualifications such as PTSD, or other broad spectrum afflictions. Simply owning a gun, same as speaking in a non-threatening Time/Place/Manner endangers no one therefore the right is protected.
Again, a paranoid schizophrenic with delusions and consistent threats of violence is not "subjectively" violent and I'm sure most psychiatrists would agree. An adult with the mental capacity of a 2 year old is also not subjectively incompetent. You don't seem to understand that mental health professionals aren't just guessing when they make diagnoses, commit patients and make other decisions. There are actual standards. Like grip said earlier, there should be limits to prevent people like Loughner from obtaining weapons.
Are you a psychologist? I learn the subject as a hobby and have some family members with mental health issues, they are broad spectrum and even delusional mental disorders have a broad range, one can have delusions, even violent ones and not act upon them or be okay with medication. Your broad brush approach is grossly insufficient.
You might be comfortable with those two people having guns, but I'm not interested in it.
Your opinion is not sufficient to restrict a right, neither is anyone else's. You MUST provide a necessary and proper argument, simply saying you aren't comfortable is not going to cut it. In the case of Laughner, it was obvious the kid was dangerous, the authorities charged with public safety turned a blind eye which led to the eventual shooting of Giffords and those in attendance of her public appearance. The gun didn't kill or injure anyone Laughner DID. Had he been barred gun ownership he would have found another way to do what he did, those with intent to injure tend to find ways of accomplishing their goals.