Anything that is highly offensive to a white liberal.
Public schools, which are run by white liberals, teach children to take offense at the most trivial matters.
Since the only people who graduate from the public school system and who paid attention in class are white liberals, white liberals constitute a growing class of people who take offense at trivial.
When you offend one of these white liberals by, for example, saying "Merry Christmas," the white liberal is trained to say "I find that offensive. It is politically incorrect to assume that everyone in our multicultural society celebrates Christmas."
Go ahead, try it! Offend a white liberal and see what happens! They all spout the same pap.