Bart wrote, typically, that for John: "Christ is a divine figure who is equal with God who has come from God to reveal the truth that can bring eternal life". Ehrman likes to contrast John's Christology with a radically different perspective from Mark or Luke, make John's a huge leap toward 4th century doctrinal solutions.
I responded: Dr Ehrman, do you not think it is actually possible that John is addressing a real or potential **misconception** within his community that Christ was equal with God, when he has Jesus saying that he is going to the Father, because he (the Father) is greater than him (Jesus)?
The point is that the author cannot be saying just that Christ is equal with God if he explicitly has Jesus saying that he is not equal with the Father. Logically then it is either
a) Jesus is both equal and not equal (somehow)
b) Jesus is not equal.
The author is not writing a compendium of different traditions. He's going for it and even explicitly writes down why it was written down this way John 20:31.
Let's see if Bart does answer though, maybe he can give the further clarification I and others have found he has often lacked on John.