I've actually been in a room full of people seriously discussing killing another person.
This was in Grenada, around Christmas time in 1983. Castro had just vowed vengeance on the U.S. for our Grenada operation. Our commanding officer, a major, had left our (remote) site and gone to the Grenada Beach Hotel (where we had tons of firepower), because he was paranoid that Castro would strike us on Christmas, and he wanted to be in a safer place than our nigh-indefensible site. What a cowardly pussy he was (although he did sneak me cold Snickers bars to fatten me up -- I was really, really skinny).
I'd brought a cassette player/recorder with me, and just for fun I put it in my uniform pocket, poked a hole through the pocket, and trailed a mic down my arm and taped it to my wrist, completely out of sight beneath my uniform. I thought it'd be fun to get stoned with the guys and record a conversation to replay the next day and laugh about it.
Well, we all gathered in a tent to discuss our plans for surviving the night in case of Cuban attack. We were all on our own, our leadership having fled to safer accomodations. That's when the conversation turned to 'fragging' our major. Not necessarily with a grenade -- a friend of mine had acquired some Soviet weaponry, a Russian .380 automatic pistol and an AK-47. Another guy had a Makarov submachine gun (I called it "The Room Destroyer"). And all of us were bristling with U.S. weaponry, of all kinds. (But it'd be suspicious if an American died by an American weapon.) So there we were, discussing gunning down our cowardly major with an AK-47, and each time the conversation would get particularly interesting, I'd let my arm dangle farther in front of me, to get better sound quality on my recording.
The next day, I played back the tape, and man oh man, did people freak out. They made me destroy the tape immediately, and I had no probs with that, so I did. I hadn't intended to record anything *incriminating*; my motivation was strictly for the humor quality, maybe get some laughs. I was always the jokester/prankster of my unit.
No one shot our major. Out of the folks who had been seriously discussing it, only one was really crazy enough to do it anyway (and he was later discharged for psychological reasons, since he really was a crazy fuck).
Anyway, just thought it was an interesting experience. Doesn't really have anything to do with free speech. I'm just a blatherer.