If one believer has no understanding of doctrinal or Biblical teaching but has an immense faith in Christ as Lord, and another believer has all kinds of book knowledge and doctrinal exactness but lacks love in their heart, who do you suppose is the most united with Christ?
The point I'm making is that there are believers in all denominations, and while they don't necessarily match up with CofC doctrine or biblical understanding I do not for a second judge their faith. I can also say that in my 30+ years in the CofC I have met far too many who have all kinds of knowledge of the "brotherhood" doctrines but wouldn't spend one second taking care of the needs of a homeless man, or a single mother of children, or an inner city youth being terrorized by gang violence and drugs, etc. They are not all like that, of course, but there are too many to be considered in harmony with Jesus.
So, who is more united with Christ? The simple believer who has love, joy, and peace in their heart because of Christ, or the one who can quote Bible front to back, but can't love their neighbor?
I know that the intentions of the CofC is to have unity based on Jesus' prayer in John 17, and to have doctrinal soundness and exact Biblical understanding, but I would prefer to be like the apostle Paul in his letter to the Philippians...
"Indeed, I count everything as loss because of the surpassing worth of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things and count them as rubbish, in order that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith--- that I may know him and the power of his resurrection, and may share his sufferings becoming like him in his death, that by any means possible I may attain the resurrection from the dead." (Phil. 3:8-11; ESV)
Paul didn't care about his own perfection through following the law, he just wanted to know Christ....the perfection that only Christ possessed. It is there that the beginnings of UNITY are found.
My two cents...
Blessings to ALL who have faith in Christ as Savior!!