Let me give you a scenario.

It is politically not correct to make fun of disabled people in a wheelchair. You shouldn't shout at them "ha ha! I can walk, you can't"

In this case, this politically correct value, is important. So I disagree with your statement:

This lesson that I learnt is why I must reject political correctness.

I think it would be fair to say, that the lesson should be this:

Political correctness does have some good qualities, in the right situations, at the right time. However, at the end of the day, we should govern ourselves on what we feel is right thought, or right behavior. The only caveat is that we also must be ready for the consequences, in the event we decide to shy away from the political correct stance on a particular topic. Not all politically correct things are wrong... however, some of them can be.. depending on the situation. Would you agree?