I disagree with you that I [or a non-Christian] cannot say who is a Christian.
What I am trying to do is to arrive at an objective definition of who is a Christian which in general is acceptable at least in a typical court of law.
As I had listed 98% [appx.] of Christians are initiated by baptism [water].
The other 2% may not use baptism-with-water but they do have some kind of initiation process which may include baptism-without-water or other formal processes.
Note I stated the above are merely formality and external processes.
But the real requirement inherent in the above formality for one to be a Christian is, one who has surrendered his will to God and will adhere and comply with God’s message delivered via Jesus Christ.
Thus an individual who has not gone through an formal initiation may still be a Christian if s/he declare s/he had surrendered to God via the Jesus Christ and be obedient to the message of the NT Gospels or gnostic gospels.
Now there should be no issue if I define who is a Christian by the above requirements.
I am sure the above definition of who is a Christian is acceptable in any court of law for the relevant cases in dispute.
Note the above is not MY non-theistic definition but a definition based on common public knowledge.
And what the heck do any of us gain if we non-Christians decide we are better authorities then other people about what kind of religious person they are. I mean, setting aside the epistemological absurdity pointed out above, I can see not the slightest practical advantage.
Nope, I did not claim non-Christians are better authorities to define who is a believer of a religion.
What I have done is to base the definition on common public knowledge on a rational critical thinking epistemological basis.
Note there is the Philosophy of Science that make philosophical sense [higher order knowledge] which many actual scientists don’t give a damn about. If non-scientist philosophers can have a rational and critical view of Science, why not philosophical view of who is a believer [Christian in this case].
The above definition of who is a Christian or a believer of any religion has tremendous implication for the future well being of humanity.
If the intrinsic definition of who is a theistic believer is one who had surrendered his Will to God and will adhere to the words of God [holy texts] delivered to a prophet/messenger,
then certain acts [religious based] of a believer are caused by the messages in the holy texts from God.
According to this principle, we can also determine whether certain negative and evil acts by believers are linked to the holy texts or not.
This is why I have been arguing the VERY terrible evil acts committed by “Christians” and “Buddhists” around the world cannot be due to the religion per se because their holy texts do not promote those violent and evil acts.
On the other hand, the VERY terrible acts committed by SOME [a very significant quantum] Muslims are influenced, inspired and compelled direct by the loads of evil laden verses from the Quran.
Therefore to prevent terrible evil religious based acts from SOME Muslims, the most effective approach would be to do something to the loads of evil laden verses or simply wean off Islam and replace it with benign spiritual practices for Muslims.
As such a formal definition of who is a believer [Christian, etc.] is very critical for the future of humanity.
If like you who do not bother to strive for a formal definition of who is a believer, you will be complicit in promoting vagueness and letting Islam and SOME evil prone Muslims continue to commit terrible evil and violent acts on non-Muslims around the world.