Are you kidding ? folks debate who is or isn't a Christian all the time. Who is one, and who is just pretending to be one for political gain or social acceptance.
Why do you think the faith has so many divisions, schisms, and so on?
Now that was the summary, Watch the ball bounce back and forth here.
https://en.wikipedia.org/wiki/Religious_views_of_Adolf_Hitler#Hitler_on_Christianity_and_.22Positive_Christianity.22
These guys can claim to believe in the Teachings of Jesus
They can claim to be real Americans and that other citizens aren't
They can claim they're saving Americans and America with their hate.
They can claim whatever they want
I don't have to take any of it as an automatic truth.
The bible itself speaks of false prophets, knowing people by their fruits, and Jesus looking at people who claim to have done all this for him and his response "I do not know you"