Of course he is stupid, but for at least the past decade he has exhibited all of the classic indications of a late stage syphilitic, as in paretic. Thus, some pity might be in order, but only a scintilla. BTW, the clinical definition set forth below omits foaming at the mouth, which symptom may raise other possibilities.
PARESIS: also called brain syphilis, syphilitic meningoencephalitis, general paralysis of the insane, or dementia paralytica, psychosis caused by widespread destruction of brain tissue occurring in some cases of late syphilis. Mental changes include gradual deterioration of personality, impaired concentration and judgment, delusions, loss of memory, disorientation, and apathy or violent rages. Convulsions are not uncommon, and while temporary remissions sometimes occur, untreated paresis is eventually fatal.
A.k.a. Acute Bidenitis?