1. Proposed Rewording:
Christianity.SE is an academic site for studying groups that self-identify as
"Christian".
And, it is perfectly valid to challenge a sect's "Christianity" - though, strictly under definitions based on Biblical bases.
2. "Self-Identifying" as "Christian" is Insufficient for Organizations:
Why is this framed as a doctrinal statement?
... please assume that the answer to "is X Christian?" is always the same as "does X self-identify as Christian?
This site should have no business in this territory, (which can understandably be perceived as an "anti-Christ", (Mark 17:21) and a misrepresentation of Christianity.
Technically, Islam "Self-Identifies" as Being Compatible with Christianity:
Muhsin Khan, Surah 57:29 - O you who believe [in Musa (Moses) (i.e. Jews) and 'Iesa (Jesus) (i.e. Christians)]! Fear Allah, and believe too in His Messenger (Muhammad SAW), He will give you a double portion of His Mercy, and He will give you a light by which you shall walk (straight), and He will forgive you. And Allah is Oft-Forgiving, Most Merciful.
3. Equivocating on What "Christian" Means - is a Misrepresentation of Christianity :
Unbelievers and even Jews know exactly What "Christians" are - or are supposed to be : "Disciples of Christ".
I suggest that challenging whether denominations are actually "Christian" - under the Biblical definitions - should be freely discussed here.
Plausibly, great discussions could occur, challenging: Mormonism - if their doctrines of salvation were not based in Scripture; or perhaps challenging "Pentecostal Holiness" - if they hold that Salvation is contingent on believing in the "Oneness" doctrine, rather than "Trinity"; or perhaps challenging the Christian Church/Church of Christ - if they teach doctrines to disobey commandments to pursue Spiritual gifts, etc.
From the Earliest Christian Histories - Baptism into the Christian faith was a very clear declaration - and to suggest "Christian is an ambiguous term" is grossly inconsistent, and dishonors what those Christians died for.
Mamrim 2:1 - A person who does not acknowledge validity of the Oral Law is not the rebellious elder mentioned in the Torah. Instead, he is one of the heretics and he should be put to death by any person.
And - because the Commandments of Jesus are held to be more authoritative than "oral law" and "traditions of men" - Christian Jews, Karaites, Sadducees, etc, were persecuted for it.
4. So - What is a Biblical Definition of "Christian"? :
Challenging the "Christianity" of a sect - defining Christianity as the imitation of Christ - is an extremely valid and necessary component of Christianity, (*and a commandment of Jesus itself, (Eph. 4:14, etc. *).
NASB, Matthew 28:19-20 - Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit, 20 teaching them to observe all that I commanded you; and lo, I am with you always, even to the end of the age.”
Following the commandments of Jesus, (being Christian) - can arguably be a fulfillment of the prophecy regarding, "the New Covenant":
NASB, Jeremiah 31:31 - “Behold, days are coming,” declares the Lord, “when I will make a new covenant with the house of Israel and with the house of Judah,
And What is it to Fulfill the Commandments of Jesus?
To love as Christ loved (John 13:34): advocating for one another unconditionally, (Luke 23:34), bearing each other's burdens (Galatians 6:2) - because: love covers a multitude of sins (1 Peter 4:8), and mercy triumphs over judgment, (James 2:13).
Note: Jesus and the Apostles gave many commandments illustrating how to fulfill this "law of Christ".
5. To What Degree Should Individuals be Accepted as Christian? :
NASB, 1 Timothy 1:16 - Yet for this reason I [formerly a murderer] found mercy : so that in me as the foremost [sinner], Jesus Christ might demonstrate His perfect patience as an example for those who would believe in Him for eternal life.
Even Paul Did Not Judge Schismatics and Traditions as "Unchristian":
1 Corinthians 1:12-13 - Now I mean this, that each one of you is saying, “I am of Paul,” and “I of Apollos,” and “I of Cephas,” and “I of Christ.” 13 Has Christ been divided? Paul was not crucified for you, was he? Or were you baptized in the name of Paul?
But - Even Paul Denounced those Who Set Aside the Commandments of Jesus for Other Commandments:
NASB, Galatians 4:21 - Tell me, you who want to be under law ...
Galatians 5:1 - It was for freedom that Christ set us free; therefore keep standing firm and do not be subject again to a yoke of slavery.
2 Behold I, Paul, say to you ... Christ will be of no benefit to you. 3 And I testify again to every man who [accepts Jewish Tradition/circumcision, etc], that he is under obligation to keep the whole Law. 4 You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.
NASB, Galatians 5:13 - For you were called to freedom, brethren, (John 8:36, Isaiah 42:7, et al);
(What does that mean? Revoke their license to pray? Ban them from purchasing Bibles? Issue restraining orders against Jesus? How is this productive?)
"please assume that the answer to "is X Christian?" is always the same as "does X self-identify as Christian?"
... From a "Christian point of view - this "doctrine" is pretty much asking people to be open to embracing anti-Christ doctrines, (Mark 13:21); B.) Certainly this could be reworded less offensively, "Christianity.SE is an Academic site for those that self-identify as Christian".