> One can argue that there's a human right to be insane, but most of us would prefer not to be pushed in front of an oncoming subway train.
This is a bit of a flawed argument-- it's not clear that people with severe mental illness are more violent than the general population, and if they are, it's not by a huge margin.
It's also flawed because we already can forcibly hospitalize people who we can prove are a danger to others. (Yes, I'm aware a whole lot slip through the cracks, but this is a resources and administrative capacity issue, not an issue of the laws we're operating under).