That’s a bit of an aside, though. We’re not talking about the specific doctrine of each sect of Christianity, we’re talking about what it means to be a Christian, in general, by definition. What’s the one thing that they all claim to have in common? Another user here explained it much better than I have but, by definition, Christians are only defined by the idea that Jesus is the son of god and that, therefore, we should live our lives with him as an example. If you don’t live by that example, you aren’t a Christian. That’s the most simplified way that definition can be formed. If we need to stay objective about it, then Christians must (again, by definition) do the things that Christ did and not do the things that he didn’t do or that he spoke against.
Some of this is starting to get semantical but the gist of it is that, if someone telling you that they’re something is best for you because it makes it simple for you, then that’s great but that’s not a sufficient barometer against which to compare any more than someone calling themselves a bicyclist can be considered one despite not owning a bicycle. This isn’t gender we’re talking about where it’s a self-actualization of one’s internal view of themselves. This is someone claiming to live a lifestyle that they either do or don’t. The entire issue, as the original article that this post is about highlights, is that Christians can vary the definition of what it means to be a Christian at will when it needs to suit their purposes because “being a Christian” doesn’t have to mean actually being a Christian. It just needs to mean that you said you’re a Christian. Therefore, you can point to anyone saying they’re a Christian and claim they’re not a “real” Christian (whatever that means). Someone else brought up the “No True Scotsman” fallacy but they actually meant the inverse of it. In the fallacy, there’s no “true” Scotsman because the only thing that defines whether or not someone is a Scotsman is whether they were born in Scotland. Similarly, whether someone is a Christian is only determined by whether or not they follow the teachings of Jesus and live by his example.