Most every US state has provision to deprive a citizen of their freedom for 72 hours for psychiatric evaluation if they pose a threat to themselves or others. So how is someone deliberately injuring themselves legal to post video of the act online? Shouldn't we discourage copycats seeking fame online and tv shows featuring online clips of such things by forbidding US websites from hosting such content?
Should we censor shows and events such as the guy in Texas that sits in a tub while handlers put live rattle snakes in with him? What about the guy that catches deadly snakes with his bare hands? And, what about shows like the jumps of Evel Knievel?
We can't lock up everyone just because they do crazy things. We would have to build many wards and hire many professional counselors to handle the number of crazy people in this country. People are going to post crazy things on the internet, and people are going to copy what they see on TV and at the movies. Besides, we have young kids that want to be the next Tiger Woods because they watch him on TV. Exposure can be both good and bad, and it's up to all of us to determine the dangers, as well as the rewards.
In my opinion, and to try to answer your question, it would have to be case by case, and not a blanket rule or law that allows us to hold someone for evaluation.