That's the difference between an obvious joke and... something different. Not that it justifies the situation entirely (or maybe at all), but would perhaps explain the reaction. Consider a similar poster who did an AMA on reddit here: http://www.reddit.com/r/IAmA/comments/1hl4gi/ive_been_raided...
After reading the actual transcript (http://pastebin.com/Ldtj6mhx), many Redditor's sided with the police.
So - not to take the side of the incarceration, but I certainly find it odd that I can't find the actual FB threat / comments (yet?).