We are run by the One Percent and their servants in the media. The only way they can control millions and billions of people is by divide and rule. They do that by identity politics and they use political correctness to quell any dissent by, as John Cleese said creating an environment which could one day lead to "an Orwellian nightmare" which is what they want because then freedom will have gone and the people will not be able to disagree with the One Percent.
So "political correctness gone mad" is done deliberately to impose control on minor issues, because if it works for those, it will work for bigger issues. If people become fearful of challenging the elites over minor issues, then they won't challenge them over major issues. So it is an incremental system of control.
As Dr Ben Carson said in the video linked to above
"it is used as a control mechanism and it is used for intimidation"
So if you don't think unisex toilets are a good idea, then you will eventually be too scared to say anything about it in case you are branded as being "politically incorrect".
Then along comes Trump, an outsider, who says "we are led by very, very stupid people" and who is the antithesis of political correctness and who says he will "drain the swamp" of these "very, very stupid people" and they are in panic because he poses an existential threat to the elites. So their media operations all call him racist, fascist etc etc to try to shut him up and slow him down, even though many prominent black people like Dr Ben Carson, Herman Cain, Mike Tyson, Don King, American black pastors, the Stump for Trump Sisters and may other people all support Trump, and even though his son-in-law is Jewish and he has many Jewish, black and gay friends.
Trump not only challenges their political correctness on minor issues, he also challeneges their big goals like climate change, he is politically incorrect over it, he doesn't believe them, and that is why they are all panicked by him and all their media teams try to mock and stop him.
Just like the elites don't like Corbyn because he is against war, so they don't like Trump because he says "wouldn't it be nice if we got along with Russia, folks?"
Trump goes against their "divide and rule", and he goes against their Syria policy of backing the Jihadis against a secular regime. One day the entire truth will come out about the pay for play charidees and Benghazi and who backed the Jihadis and who funded Isis and who promoted the divide and rule that caused so many problems across the world.