It is beginning to look as if the USA searches first for the true meaning of the words used, and then addresses that found meaning, if I correctly read the above.

The UK does not do that. It searches first for the for the legally available meanings of the word. Plainly the legally available meanings of the word "anti-semite" include the meaning that the object of the word is in fact an anti-semite.

Similarly, in the UK, in order to justify an accusation that a person is a liar you must show not merely that they have told a lie (perhaps in relation to the subject of controversy) but that they are a habitual liar, for that is an available meaning of the word "liar".