You can't choose who is offended - true. If a gay couple kissing offends you, that's your problem. If someone saying grace at a restaurant offends an atheist, that's their problem. If someone is breast feeding, mind your business.
You don't need to change because people are offended - subjective. If you tell a joke and a ton of people are offended, maybe you should ask yourself if maybe it isn't crossing the line.
Choosing to be or not be politically correct is what it is. If you are telling a dirty joke and realize that a little girl is nearby, you would possibly choose not to tell that joke at that exact moment - because you don't want to offend the child or mother. Is that a compromise of your morals, or just being sensitive to what's going on around you?
If you see a woman driving with her children unbuckled, you would probably choose to say something even though it might cause offense.
If you are willing to compromise your morals due to political correctness, they weren't really strong morals to begin with. My point is, be or don't be politically correct, but use the term properly. It is just trying not to be offensive. There is no direct moral correlation between being or not being politically correct.