In the fairly recent past it was a liberal topic of discussion, banning hate speech to "protect" minorities who might be offended. The UK has banned hate speech, resulting in some preachers being arrested for saying that homosexuality is a sin (most were released, charges dropped). Germany has banned the nazis and all memorabilia, something I dont like but am loathe to attack them over.
In several nations in the EU holocaust denial is illegal
http://en.wikipedia.org/wiki/Laws_again ... ust_denialThese laws ban spreading certain ideas because they have been deemed offensive.
In the US the courts have ruled time and again that the ideas that offend might be the most important ideas of all.