Ultimately whether it is humane or not is irrelevant. If you are trapped on a lifeboat with a bunch of people, and one of them is mentally ill and threatening

Ultimately whether it is humane or not is irrelevant. If you are trapped on a lifeboat with a bunch of people, and one of them is mentally ill and threatening the safety and survival of the other people on the lifeboat because of an ability to regulate their own behavior, the people on that lifeboat are justified in taking whatever action necessary to ensure a safe environment. Society is that lifeboat. We should do everything possible to offer mentally ill people the resources they need to help themselves and to integrate themselves into society. But if that fails, and they are unwilling or unable to integrate into society, and their behavior causes a safety risk and/or a significant disruption to society, then society is completely justified in using whatever measures are necessary to ensure they aren't a danger to others. It is simply absurd to suggest (as many do today) that profoundly mentally ill people should be allowed to roam free and manifest their mental illness in ways that are harmful to other people because it it "inhumane" to stop them.