The Director of Public Prosecutions, Sir Ken Macdonald QC, delivered a lecture with the above title at Birmingham University on 4th March. The full text is here. It is an extremely interesting exposition of the Crown Prosecution Service's - surprisingly liberal - approach to putative offences involving freedom of expression, and stresses the crucial importance of the 1998 Human Rights Act in bolstering the legal protection of free speech.
As the DPP points out, while there is no universally agreed consensus over what is acceptable and unacceptable, widely held views change over time, and the law needs to respect this and to evolve accordingly.
"A reckless inciter of violence imprisoned in one generation is a martyr to free speech in the next.
"For our grandparents a gay marriage would have been an abomination. To our children it is the excuse for a great party."
Anyone interested in free speech issues should read this illuminating reflection of the official mind.