This is the dirty secret of Christian Nationalism: They don't think many of their fellow Christians are really Christians. For example, Catholicism is the largest denomination in the US (about 20%), but many conservative Christians (particularly Baptists) don't consider them to be "True Christians."
Mrs. Betty Bowers
(📢) BREAKING NEWS: Donald Trump's Pentagon Has Just Declared Mormons Non-Christians, Spitting in the Face of a Voting Bloc Whose Loyalty to Trump Now Seems Like a Successful Long Con By the Serial Rapist, Atheist, and Notorious Hater of Organized Religion
LDS Church left off Department of Defense’s list of Christian religions.