Political correctness causes people to censor themselves. It can also stop important information from being told to the masses (Example: Obama refusing to call the Orlando terrorist a radical islamist.). Political correctness also violates the 1st amendment.
Political correctness should not be taught, as it can cause nearly an entire generation to be oversensitive. Just look at all the SJWs that colleges have thanks to the teaching of political correctness.
Finally, political correctness ruins comedy by censoring certain comedians for jokes that they made. Nowadays if you dare to make a joke about black people then you will be censored.
Overall political correctness is a codeword for censorship. It isn't benefical to America.
PC causes people to silence them selves unnecessarily and to silence people who disagree with them. It causes people to be afraid of other ideas and facts that do not fit their narrative. It stops important conversations from happening because those conversations might offend someone. It is very very harmful.
First of all, Political Correctness completely contradicts the idea of Freedom of Speech; the First Amendment clearly states that the government shall not abridge it - if such is the case, why are everyday citizens attempting to abridge it?
Secondly, teaching it to children is to teach them lies. From a very young age, we tell kids that the world is a tough place to live in. Telling them not to say something is telling them that they must be sensitive to other people - in which case, they won't be prepared to go head-on with those who don't "watch their language." If we're going to prepare kids for a tough world, they need to be able to take blunt commentary - "offensive" or not.
Thirdly, people might actually get more offended by PC than bluntness itself. We watch what we say because it MIGHT offend someone, without that individual coming up to his and saying "shut it." We have our language, they have their choices.