His theology is not Christian theology.
But I am not in the position to judge his salvation, whether he "believes in his heart". That's why I have not said "you're not a Christian", and I won't. I don't know that. I do know what he is espousing is wrong, Biblically and theologically.
As to your last point: I never understand why the Christian religion is supposed to just accept any theology that espouses itself as "Christian". People say they're "Christian" if they put up a Christmas tree, and that's the most harmless example. People say they're Christian if they believe Jesus and Satan are spirit-brothers (Mormon) or if their founder was a lying pedophile philanderer (Mormon).
There is a whole Book--the most popular one in history--that details Christian theology. We don't have to accept anyone that slaps a label on whatever belief suits them and calls it "Christian". That's not even loving. It damns a lot of people to Hell.