Christian "purpose" and "meaning" in life.

[Tonus]

Till you get to the atheist part I can accept those things, I can check those out. However how am I suppose to check out what you feel, by your actions and speech. Atheist tell Christians we can't tell whither an person is a Christian or not, we say we can by their speech and actions, but that doesn't seem acceptable to atheist, so why should I grant your claim to be an atheist by your actions and speech, as you note below.

I think the difference is that we would judge a person as being atheist or not based on a single criteria: do they believe in god(s). There can probably be areas of quibbling, but that's the gist of it. We see Christians from various denominations claim that other self-identified Christians are not Christians at all, and those will make the same claim right back. Some people claim to be Christian but not members of any particular religion, using the Bible as their guide and avoiding any other affiliation. Nearly every Christian that I've seen, regardless of denomination, could reference scripture to explain why they were true followers of Christ and why others were not.

For JWs and Mormons (and similar groups) it seems easy to disqualify them, as they have either added to scripture or modified it to support discordant beliefs. But most Christian denominations only use the Bible and so the differences between them is down to interpretation. Your stated view that a person's devotion to Christ is more important than any affiliation is the most sensible one to me, but probably not to other Christians and faiths.

It's not that I don't think you are a Christian, but that so many Christians seem to assume the authority to deny the legitimacy of others, and vice-versa.