Whhatever that stupid message was, it wasn't terrorism nor a threat to commit terrorism.

Essential to the definition of terrorism, whether by individuals, groups, or governments, is that the violence directed at members of the public involves an intention to influence the way people think and behave.

Exactly. This wasn't a terroristic statement. At most it might be prosecutable as a threat to public safety, but definitely not terrorism. That's why this is an attack on the First Amendment. Going back to the original post, as Thurgood Marshall said, "the First Amendment means that government has no power to restrict expression because of its message, its ideas, its subject matter, or its content."