Joh 8:28 is one of many passages that, to me, indicate very simply and straightforwardly that Jesus and God are completely separate entities as JWs teach. Other passages indicate that God "sent" Jesus, "approved" of him, "loved" him, etc. Such language logically indicates that they are separate and distinct. Wasn't the Bible supposed to have been written in a way that would be clear to the masses, to common people? To try to make such passages harmonize with the Trinitarian view requires mental gymnastics that are beyond the ability of the common man. Why would the master teacher, Jesus, speak in such an esoteric way, a way that would misrepresent or cause people to believe wrongly?
I have thought about this a lot lately. My only answer to that question would be that maybe he was intentionally speaking in a way that would hide the real truth in order to see who would dig deeper and put forth effort to arrive at truth... sort of like the way he did with parables; he would speak in parables to see who would come back to him and try to figure out what he really meant.... to see who was really interested and would put forth effort to find truth.
My current belief is aligned with that of JWs. I don't believe Jesus was hiding anything with his language; I'm just exploring that option. To me, the great bulk of the NT shows the separateness and distinctness of Father, Son, and holy spirit. Consider Mt 3:16,17:
As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, “This is my Son, whom I love; with him I am well pleased.”
How could this passage allow for the Trinitarian belief? It shows all three elements of the so-called Trinity in three different places at the same time. God was in heaven, Jesus was on earth, and the holy spirit was in between ("descending"), all at the same time. That, to me, just makes it clear that they are separate and distinct. Also, God said he was "well pleased" with Jesus; doesn't that logically indicate they're separate?
P.S. A few weeks ago Sea Breeze, mentioned on this site Joh 2:19-21:
Jesus answered them, “Destroy this temple, and I will raise it again in three days.” They replied, “It has taken forty-six years to build this temple, and you are going to raise it in three days?” But the temple he had spoken of was his body.
I have given some thought to that, the Trinitarian argument being that Jesus resurrected himself (or at least his body?). That is, to me, one of the best Trinitarian arguments. I even looked at the Greek to see whether the verb (in "I will raise it") was in the passive voice so that it could mean "it will be raised," but the verb is in the active voice, so it should be translated with an actor (indicating someone performing action) as in "I will raise it," not "it will be raised" which does specify the actor.
I'm still pondering this passage. However, right now I feel that the overwhelming bulk of the evidence shows that God and Jesus are separate. I think of this: Suppose a wreck occurs at the big intersection and 997 out of a 1000 eyewitnesses say the traffic light was green, but three say it was red. I think it would be reasonable to be assume that the light was green and to try to figure out why the three said it was red. Was the sun obscuring their vision? Do they have some kind of color-blindness? Are they lying?
I think of Trinitarian "proof texts" as being like the three witnesses in the illustration above. I completely grasp the Trinitarian argument in connection with Joh 2:19-21; I'm just trying to explore the passage in the context of the entire NT (the 997 witnesses) and what I consider to be the overwhelming evidence concerning the nature of God and Jesus.