I need to see it. It's evident that identity is important to many conservatives, even on INGO. There was a thread recently in which a few people argued in favor of the idea that "identity" is important. I don't really see those who argued such as white nationalists. So I think it's possible to be an identitarian of sorts who happens to be white, and not be a white nationalist. I don't really know anything at all about the "Identity Movement". And I've never heard about this church you're talking about. Are they white nationalists? I still don't know with any certainty.
Maybe it's just me, but I see the terms "white nationalist" and "white supremacist" used interchangeably, and I don't think that's necessarily valid. One can be a "nationalist" (ie. pro-USA - or whatever your nation of choice is) regardless of race. A "white supremacist" is pretty specific - one that thinks the white race is superior (supreme) to other races.