I never understood this. Basically every country, including the US, has libel and slander laws, and almost the same everywhere in the West. People were thrown to jail even in America for "a single tweet", the exact same way as in the UK. And for example, saying that you support violence in specific cases, like there is an ongoing riot, and you tweet "kill them all", that's not protected by any free speech laws in the world, not even the American, or any states' in America.