There's more to it than just theology. They actually seem to regard chrstianity as a religion created by and primarily applying to people of European descent. It's as if Europeans were either the "new Israel" or the "true Israel" (with actual Jews as evil counterfeits, G-d forbid).
And there are plenty of anti-Israel Protestant "reconstructionsts" in the JBS too. In fact, the man who invented the explicitly anti-G-d, anti-Bible religion of "creativity" (Ben Klaassen, mach shemo!) came out of the Birch Society!
You’re describing so-called replacement theology. That’s the heresy that won’t die, at least yet.
They are intentionally overlooking that in the Christian faith one is grafted into the choice older vine, rather than setting independent roots.