Reply #14: No, "true Xian" isn't necessarily a meaningless term.

[Igel]

As commonly used, it serves as a distinguisher between those the speaker judges to be good and righteous (or whatever the metric is) and those disapproved of. It's semantics involve attitude and evaluation and are therefore really tricky to represent in a simple manner.

It's like "good person." It's not semantically vacuous; it's just so subjective a phrase as to be undefinable apart from a detailed knowledge of what the speaker judges to be "good".

Ultimately, if you're a Xian, the judgment isn't your own but God's/Jesus', but that's only because God's judgment is taken to have a rather different status than a person's private judgment.

In any event, "Christian" is, by itself, fairly ambiguous. There are lots of definitions but most don't feel permitted to apply them. Those who do are considered rude and boorish. Muslims don't engage in takfir, and neither do Xians. In both cases it means that all that's left is a very basic definition--the least common denominator--and you're forced allow those who you really don't want share a designation with into your group. If you don't decry the 9/11 attackers as non-Muslims, they're left being Muslims; if you don't want to say that the abortion clinic bomber wasn't a Xian, then he shares your faith. You make the distinction and it's boorish. So you're left with saying not that so-and-so isn't a Xian/Muslim, but not a "true" or "good" Christian or Muslim. Civility.