It is fit-and-proper and legally/constitutionally-sound that someone should be declared "Dangerously Mentally Ill" only after a fact-based and contested hearing before a judge-and-jury, in accordance with our 1000 year old system of laws and our Constitution. Why? Because to tag any citizen as being "dangerously mentally ill" takes from such citizens as many civil and political rights as a conviction of a felony---And, deserves the same legal protections.
At this time there are too many government units (eg -- The FBI) who will accept the unverified and non-judicial comments of some (Anonymous?) Psychologist/Psychiatrist/Other-persons as sufficient "Proof" to deprive citizens of a basic civil right. Even super-sane me (If, and only if, you accept my self-diagnosis) once consulted a psychologist, with my wife, to iron out some marital problems---Which smoothing did occur. .
Should I or some child with home/school problems who sees a school psychologist or some active-duty member of the Armed Forces/Veteran for whom war/other-problems has resulted in s/he seeking counseling, and other like and law-abiding citizens be deprived of a basic civil right without "due process of law"? [I believe we have another, of too many Federal Laws which provides for both criminal and civil prosecution for "Deprivation of Civil Rights Under Color Of Law" which should deal with and punish those who would do so to those who are not dangerously mentally ill.
The FBI has reportedly placed entire groups of innocent military veterans on the "no buy" list and that without "due process of law".