Perhaps it is time to require action. When a school or business feels the need to protect itself from someone who is mentally ill, perhaps it should be required to try to protect others, too.
Thus, if a school or a business ejects or otherwise removes a student or employee out of concern about behavior and dangerousness, the principal, dean, or head of the Human Resources department would be required, under a mandatory reporting law, to inform the medical director of the appropriate public health jurisdiction. This public official would then have to initiate an evaluation which might lead to a face-to-face evaluation and, depending upon its outcome, possibly involuntary treatment.
Precedents exist. There are mandatory reporting laws for child abuse. Teachers and medical professionals cannot just look the other way when they see a child with multiple, suspicious bruises. The same logic applies here: a severely ill person battered by psychosis should not be left at the mercy of a condition that causes others to be worried for their safety.