What do you think of Political Correctness?

The problem is that it almost immediately became used as a derogatory term because of a few ridiculous examples (not allowing the word blackboard, for example). As such, some people seem to think they can freely express obnoxious views without criticism, and people who object are derided as ridiculously left wing - "it's political correctness gone mad", often in an aggressive and bullying manner. Some PC things are silly, but the premise of not wishing to offend is applaudable. Some people do seem to keen to be offended on other people's behalf, these people are often the ones that give political correctness a bad name.