Political Correctness is an attempt to redress wrongs committed against those who have been disadvantaged in society as a result of discrimination, or percieved differences (gender, sexual orientation, ethnicity, religion, disability).
Notice I did not add 'race' to that list; 'race' is a social construct -- it does not exist in any biological sense, only in a social sense. The only differences amongst human beings are the artificially drawn lines between 'us' and 'them' for whatever reason. In terms of genetics, only a minute number of genes are responsible for skin colour, and there are far, far more similarities amongst humans than differences.
Thus, political correctness in itself is not something to be jeered at. on the one hand, I understand people getting upset by this and there have seen instances where what has been served under the title of PC ammounts to little more than thought policing. However, that 'pc gone mad' line trivialises an important goal and seems to miss the point of political correctness, which seems to me to be two-fold: avoid offending people, and don't discriminate. I don't think there is much that is 'mad' about that.
What should be examined here instead are the attitudes that expose racism, something which indeed does exist. By racism, I mean having or demonstrating the mistaken belief that there are biological or other differences amongst human groups that separate 'us' from 'them', including this notion of 'own country', as well as the idea that 'they' do it to 'us'. As so many posters have said, who exactly are 'we' and who are 'they'?
Lastly, just because someone has had contact with a person of another ethnic or cultural background does not mean that they do not harbour beliefs which are inherently racist or xenophobic. Neither is it an excuse to say that someone is just ignorant rather than racist. Racist attitudes should be challenged and the underlying attitudes exposed.