What we need to is make it clear that suicide is your right. Treatment should be completely voluntary at all times. I would wager that the possibility of being restrained for days or weeks prevents many people from seeking help that could actually have made a difference.
No, it isn't your civic duty to take the right to suicide away from someone. It's your duty as a friend and a human being to be a non-judgmental ear and shoulder. But in the end you have to respect their rights as an autonomous being.
Emergency visits are not about locking someone away but about figuring out a best treatment. Whether a person will follow the treatment or not that's a different story but at least someone was there for them, to listen, to help, and with means and experience to do it.