The big problem with this is the request (demand) for blanket information versus specifics.
For example, if a specific poster or two or ten made a specific threat, that is absolutely something that would be justified under the law to provide.
However, if all the information on 6,000 members of a group were requested (demanded) even though only two or ten made specific threats, that would violate every legal precedent in regards to this.
For example, imagine 5 years from now if some troll came here and made a lot of threats against President Oprah. That person's information could be requested via subpoena. However, if President Oprah demanded the user data of not just the person who made the threat, but every single member and everyone who visited, that would be a violation of the law.