There are two kinds of Christians, the Bible studying kind, and the one who hearsay. Philosophical arguments like this are handled extensively in the field of (Christian) theology. There are many things many Christians claim nowadays are not biblical. Imagine “physicists” start claiming things that no falsifiable, tested theories in physics attested to. Now do you call them physicists? If there are enough majority of them is doing it, do you say “physicists“ (as a generic term) now believes in so and so? This the kind of situation that’s happening in Christianity. Because, the core believe is anyone can be a Christian (subjected to minimal check such as the basis of their salvation, some also include baptism), unlike in physics you need to be trained and qualified. I’m not saying that’s right or wrong. But I’m pointing out the situation, so that one can understand, for outsiders one would say “Christian believe this or do that”, and for the “insiders” who really study the Bible and trained in theology and know differences between denominations for example, would be completely puzzled and say it is not.

I guess the former focuses on Christian as a social construct and includes whoever claim to be Christian or even influenced by Christian thinking. The latter focuses on Christian as what it is ought to be and knows that all are sinners, including Christians, and I’d fall short of the standards the Bible uphold. Among these Christians, they know that the majority of Christians has gone astray.