Using offensive, abusive, or insulting language is a criminal offence in the UK, under Section 5 of the Public Order Act.
(This law applies even if it’s printed on a T-shirt. According to the BBC one shopkeeper was threatened with arrest for displaying a toddler’s T-shirt in his shop window that had the slogan: “Winner of the egg and sperm race.” Although FCUK French Connection UK) found a way round this, their slogan upset the Advertising Standards Authority (ASA), which upheld 26 complaints about the logo. However, it was eventually allowed in adverts after being registered as a trademark. Where there’s a will there’s a way.)