It is not Truth to say that “according to the RCC, people who reject its authority cannot be real Christians”.
If something is said about Catholicism, what is said should be true and not false.
If something is said about Catholicism, what is said should be true and not false.
If you think what I said was untrue, it means you are either that you don't know RCC doctrine very well, or you are lying. It's as simple as that.