A wise lady once said..."God has not committed to any finite man the work of judging others, for man's judgment would be biased by his peculiar traits of character. Neither had He laid it upon any man to bind the conscience of another, or to pass judgment upon His holy Word, defining what is inspired and what is human. Unless sanctified, soul, body, and spirit, man will be in danger of manifesting an unkindly spirit toward his brother who does not agree with his ideas. There is no such narrowness with God".
The truth is that while scripture does speak of three divine beings, the trinity doctrine goes way beyond what the NT teaches and the formula that the various creeds have cobbled together are nothing else other than speculation.
"The doctrine of the Holy Trinity is not taught in the OT. In the NT the oldest evidence is in the Pauline epistles, especially 2 Cor 13:13 and 1 Cor 12:4-6)" (New Catholic Encyclopedia, Volume 14 page 306, Trinity, Holy (in the Bible)
Here is the point blank denial of the trinity doctrine being found in the Old Testament. This is even though some trinitarians maintain that there is evidence of it there. Notice here that what is said to be found in the New Testament is not the trinity doctrine itself but ―evidence‖ of it. As we shall now see, the same is said with regard to this teaching being found in the gospels. The encyclopaedia continues
"In the Gospels, evidence of the trinity is found explicitly only in the baptismal statement." (Ibid)
This is quite a remarkable statement, particularly as it was the Roman Catholic Church that made it. This is because they regard their rendition of the trinity doctrine as the central belief of their denominational faith (also of Christianity). Notice it says that even then it is only evidence that can be found in Matthew 28:19 and not the trinity doctrine itself. This is the only text in the Scriptures where it actually names Father, Son and Holy Spirit (Ghost) together as such. We can see therefore that even the Roman Catholic Church admits that the trinity teaching is only an assumed doctrine, not one that is explicitly stated in Scripture.
Based on the above, how can any church or individual claim one is not a Christian if he/she does not believe in an assumed doctrine?