Here's a classic Judge Reinhardt opinion. It's joined by Chief Judge Kozinski and reverses the conviction of Walter Bagdasarian for posting some indisputably nasty, and arguably threatening, comments about Obama posted online. (Read the opinion for details; I won't post the comments here because they're racist in the extremis.) But it does so with a plethora of extraneous -- and yet relevant -- details about both history (e.g., vitriol used in previous presidential elections) and contemporary matters (e.g., other slams and rumors about Obama and the status of race relations in America).
Ultimately, the Ninth Circuit holds that an objective observer wouldn't have taken the comments as an actual threat and that Bagdasarian didn't have the subjective intent to actually harm the guy either. Just a big talker.
Judge Wardlaw dissents. Her opinion, as well as the majority opinion, are definitely worth reading in their entirety. I particularly thought it characteristic that Judge Reinhardt wasn't afraid to reveal his opinions about Bagdasarian, saying that he was "an especially unpleasant fellow" whose comments demonstrated his "own malignant nature," and yet reversed his conviction.
It's a tough call what you do about threats like this. On the one hand, you have to take them seriously, as there are lots of nuts out there, and you never know when you're dealing with an actual shooter. On the other hand, 99% of them are just pos(t)ers. Harmless. Whose speech is just masturbatory violence.
Good opinions all around.