Trumpers characterize trans people in sports as guys in wings who pretend to be girls so they can beat up on them. 

The fact is that men's sports are where the highest levels of both competition and compensation are and trans people are unfairly locked out of these opportunities. 

But the most offensive thing about this point of view is that it implies that trans people come out as trans on a whim or to gain some kind of advantage, completely ignoring the challenges and often physical danger trans people face when they come out.

Maybe Trump supporters get it, maybe they don't, but they certainly never fail to take the most hateful, disingenuous, dishonest position about every issue that involves trans people or LGBTQ rights and protections.