political correctness can be right-winged too. For example, you can't criticize cops, Israel, capitalism, the USA, or religion. They can be just as intolerant, if not worse. 
Trump's birther thing was caused by his immense jealousy: that a black man with a muslim father, who grew up in various parts of the world, was  the president when HE wasn't. I doubt it was racism. Trump is a petulant adolescent.