When you say someone is being 'politically correct', what do you mean by it?

Do you use it as a kind of shorthand for ‘intellectual dishonesty’? That’s what it brings to mind when I hear (or see) the phrase used in a negative manner after someone says something like “I believe XYZ”, or a statement that includes newer, more respectful terms for certain groups of people. (“Oh, you’re just being politically correct.”) Is that interpretation accurate? Does it indicate that you don’t think anyone could actually feel that way, so they must be fooling themselves or others by saying the politically correct thing? Or what, exactly? Are they still being ‘PC’ if they really do feel that way?

Bonus question: What’s so bad about being PC, anyway?