Shouldn’t expulsion be adequate?
Lawyers are making anything logical, common sense or preventative into "bigotry", "discrimination" or "hatred." It's an enormous cash cow for them.
On the practical level, the psychology of violent mental illness is such that when the person with the damaged ego is rejected, for whatever reason, that is the time they choose to unleash the violent retribution. This is why many women end up staying with batterers, or having to go into shelters if they manage to expel them from the home. Most domestic killings occur just when the woman manages to enforce the separation.
So in the VT case, expelling Cho might have had the same result as what did happen. This boy was now looking at graduation, leaving a familiar environment in which he was at least tolerated, and having to go into a new environment where he would be looked at as weird and rejected again, this time with higher stakes. He had a psychotic break, taking the symbols of his oppression -- well-adjusted kids -- out with him as he committed suicide.