Before we go any further into our discussion I would like to say one thing. I do not use belief in a Trinity God as the basis for fellowship or to determine if one is a Christian or not. Understanding the Divine nature of God is a complicated subject and should not be used as a basis for fellowship or to determine if one is a Christian or not. I believe we need to use a common denominator to base fellowship on and that common denominator is found in Matthew 16:15-17.
Matthew 16:15-17 Jesus said to them, “But who do you say that I am?” Simon Peter answered and said, “You are the Christ, the Son of the living God.” Jesus answered and said to him, “Blessed are you, Simon Bar-Jonah, for flesh and blood has not revealed this to you, but My Father who is in heaven.
Belief in Jesus as the Christ, the Son of the living God, should be the common denominator for all believers. Anything after, Jesus is the Christ the Son of the living God, the waters get muddy so we should never use something that is unclear as a basis for fellowship or identity.