It's more than just a death threat, the person killed in such a manner would surely generate a human-sized pile of Ice 9, which would pose a much greater threat to humanity than any AGI.
If we're seriously entertaining this off-handed remark as a measure of Altman's true character, it means not only would be willing willing to murder an adversary, but he'd be willing to risk all humanity to do it.
What I take away from this remark is that Altman is a nerd, and I look forward to seeing a shaky cell-phone video of him reciting one of the calypsos of Bokonon while dressed as a cultist at a SciFi convention.
