I was reading a discussion on a forum in the UK that was discussing this, and I realised that I'm of course entirely familiar with the expression, but I don't really know what it actually means.
One writer there, who is a lawyer, commented as follows:
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'A lot of people seem to still have a problem with the concept that for 'freedom of speech' to have any value it has to include the right to give offence by saying things that others disagree with. Redmond-Bate v Director of Public Prosecutions* is my favourite legal ruling. In it the judge says 'Free speech includes not only the inoffensive but the irritating, the contentious, the eccentric, the heretical, the unwelcome and the provocative provided it does not tend to provoke violence. Freedom only to speak inoffensively is not worth having'. But he had also commented on the specifics of the case that 'Nobody had to stop and listen'.
* http://en.wikipedia.org/wiki/Redmond-Bate_v_DPP
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I'm not suggesting this is a topic for discussion, but I thought it might prove thought-provoking for others.