Clearly, someone in England needs to start paying more attention to what people are charged for. This episode makes it seem like someone seeks nothing more than to fill as many cells as possible, as opposed to achieving justice for actual crimes. "We don't know what's on this Facebook user's computer, therefore he's a threat to national security. Let's take advantage of this and fill one more cell." I do hope people start rioting over this, as only a ridiculously angry mob can prevent such atrocities in the future.
Personally, I think the real reason why this is happening is because he encouraged people to insult dead law enforcers. This is nothing more than payback. How dare he think he could get away with using free speech. He can't be a threat against national security, since there is nothing to secure the nation against it's own government. You can't threaten something that doesn't exist. He may as well be threatening to kill those living in British-controlled Mars colonies.
BTW, although I've never read these posts or (supposed) cyber attack warnings, I can't say I would likely agree with them. However, I do 100% agree with Christopher's right to say what he wants, when he wants, where he wants, how he wants, and above all if he wants, and who he wants to speak to.