I distinguish from the broad Christian tent, what I personally believe the faith once delivered to the New Covenant people of God exists in, which I find limited to that commanded by Jesus to be observed and that alone, therefore not going beyond the New Covenant teachings. For me it is the 1646 First London Confession of Faith with the addition of the "Principle of Regulative Worship", you don't add to or take away from the faith once delivered. So, I reject the idea that the faith once delivered includes musical instruments in the assembly, the Christian calendar with its Easter and Christmas Holidays, women speaking in the assembly or taking the rule over men in any realm of life, Sunday Schools, the office of evangelist, the idea of mission boards, the application of the so-called "Great Commission" to today, etc. But, I do not narrow my idea of the Christian tent to my beliefs.

I exclude from the Christian tent those who deny that God is one; and that this one God exists as three separate but equal Persons. Yet in the working out of redemption, there are offices or roles where there is an order: Father, Son and the Holy Spirit. Any denial of this puts a religion outside the bounds of Christianity: thus Unitarians, Oneness Pentecostals(?), JWs, Mormons, etc are not Christians.

Even among those claiming the Ecumenical Creeds, there are those I consider outside the Christian tent, and I meant the Orthodox and Roman Catholic Churches. They are both rank works salvationists placing man's traditions on equal footing with God's word, a spurious salvation. By their works you shall know them, and this history of one the Popes is an eye opener:

Pope Sixtus Quintus IV -
"Sixtus founded the Spanish Inquisition through the bull Exigit sincerae devotionis affectus (1478)...According to the later published chronicle of the Italian historian Stefano Infessura, Diary of the City of Rome, Sixtus was a "lover of boys and sodomites", awarding benefices and bishoprics in return for sexual favours and nominating a number of young men as cardinals, some of whom were celebrated for their good looks." https://en.wikipedia.org/wiki/Pope_Sixtus_IV

The SDA & Church of Christ (Campbellites) I place outside the Christian faith for their violation of salvation by grace alone and adding a law to the gospel of grace. The SDA with their Sabbath requirement and the "Investigative Judgment" which is a spurious law salvation. The Church of Christ claiming to be the one church outside of which there is no salvation, and in addition making baptism a law which one must obey for remission of sins, again a spurious salvation.

It becomes trickier for me when considering the Arminian oriented groups. I consider the older Methodist types, followers of John Wesley to be within the Christian tent based on John Wesley's commentary on Eph. 2:8-10 for one point, and I quote from Wesley:

Verse 8
For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:

By grace ye are saved through faith — Grace, without any respect to human worthiness, confers the glorious gift. Faith, with an empty hand, and without any pretence to personal desert, receives the heavenly blessing.

And this is not of yourselves — This refers to the whole preceding clause, That ye are saved through faith, is the gift of God.

Verse 9
Not of works, lest any man should boast.

Not by works — Neither this faith nor this salvation is owing to any works you ever did, will, or can do.

Verse 10
For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.

For we are his workmanship — Which proves both that salvation is by faith, and that faith is the gift of God.

Created unto good works — That afterwards we might give ourselves to them.

Which God had before preprepared — The occasions of them: so we must still ascribe the whole to God.

That we might walk in them — Though not be justified by them.

The Pentecostals and Charismatic teachers of today, claiming descent from Wesley, I put outside the Christian tent based on their obvious corruption similar to the old reprobate, Pope Sixtus Quintus IV listed above.

When it comes to Dispensationalists and Theonomists, I consider them borderline because each in their own way wish to return to the Law of Moses which I find heretical to the point of blasphemy!

Yet, I on the other hand consider the danger of being a Pharisee and thinking one group has a lock on the truth and all others are outside the faith. John told the Pharisees and Sadducees, "and think not to say within yourselves, We have Abraham to our father: for I say unto you, that God is able of these stones to raise up children unto Abraham."

I worry about judging in the more questionable areas. I believe the Arminian, the Methodist Adam Clarke is within the Christian tent, but I find he often gets tangled up in faulty logic trying to keep man to our responsibility.

I believe those who reject the common salvation taught in the old confessions of the Reformed, the Lutherans, Anglicans, Baptists are outside the Christian tent.