(1) A person who uses threatening, abusive or insulting words or behaviour, or displays any written material which is threatening, abusive or insulting, is guilty of an offence if—
(a) he intends thereby to stir up racial hatred, or
(b) having regard to all the circumstances racial hatred is likely to be stirred up thereby.
(2) An offence under this section may be committed in a public or a private place, except that no offence is committed where the words or behaviour are used, or the written material is displayed, by a person inside a dwelling and are not heard or seen except by other persons in that or another dwelling.
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However, it looks as though you might get away with saying some very nasty racist things in public if you were careful with your vocabulary, tone of voice and so on.
Is there any protection for people with Tourette's or mentally ill people, I wonder?