Don't kid yourself. There will never be a cure for all mental illnesses and we will never stop mentally ill people from harming other people. I'm all for helping the mentally ill, and searching for solutions, but there won't ever be a cure for mental illness any more than the life span of humans will ever in the future extend an another 10 years.
We can make mentally ill people less dangerous, to others, if not to themselves.
The problem is that everybody thinks an attack by a mentally ill person won't happen to them. Almost all of them are right. And who gives a shit about other people?