Bigots have principles that are guiding them. Bad principles, misguided principles, but principles nonetheless.
The sad thing is, President Trump has no principles, except for self-aggrandizement.
Trump isn't doing this out of bigotry. He has no feelings about GLBT people, one way or the other. He's throwing transgender servicemembers under the (MRAP) bus out of self-advancement. He thinks it'll make his religious base happy.