First, do I think what he did was probably meant as a joke, yes. However, Terrorist threats against schools, is not something to joke about, especially in a public forum. Let's say this guy was about to snap.. (it's happened) and the police did nothing, you'd be all over them. There are so many "can't win either way situations", like the TSA and flight protection. I don't know all the facts, nor do I really want to, other than a few articles. Needless to say, it's out legal system that's made this even bigger. I actually believe the arrest and search was warranted. The 5 months and $500K, no.. I hope he does get off with time served, which I suspect he will. Or even better found not guilty, but he unfortunately DID say those things.
This isn't a first amendment thing, you can't say anything you want. As someone else mentioned, FIRE in a movie theatre, threats against the president, etc. There is too much insane trash talk these days anyway, the internet is not a place you can expect to say anything and hide, people try, some succeed, but use your head.. Once it's posted, it's there forever! like this.. NO!!!!!