If the unitarians held to otherwise normal doctrines and they could make a convincing argument, then they could be probably be viewed as part of the same Christian family. The problem with quoting verses spoken to the apostles is that they were a narrow group in a narrow era. It does not automatically apply to those who may not be Christians at all (or are heavily deceived).So, the very sad result of a heated debate between Trinitarians and Unitarians, is that we convert this in a battlefield of people defending their relationship with Jesus, versus people defending their relationship with the Father.
A battle of loyalties.
This is the WORST result ever possible!!!
Jesus said "My Father and I are one".
So, by imagining ourselves as opponents, we are placing our egos over the special bond between Jesus and His Father (whatever this bond is in theological terms) that should be the bond that we nurture among us.
I can't fathom the exact nature of the bond between Jesus and Our Father. What I know is that Jesus expects the bond bewteen all members of the Forum to be as strong as that kind of bond.
I do not pray for these alone, but also for those who will believe in Me through their word that they may all be one as You, Father, are in Me, and I in you- May they also be one in us, that the world may believe that You have sent Me. (John 17:20,21)
The unitarians really should cover all the verses about the deity of Christ and explain why those are not true. Okay. they should explain those verses so that others can see the arguments and decide against the Trinitarian view if convincing. All that is done typically is people share some passages about the humanity of Christ, which is not an issue in conflict. Also, the alternative views of verses listed by TomL were pretty mush incomplete and insufficient to deny Christ's deity. So the Unitarian viewpoint does not appear sustainable.
The effect has been essentially to lend greater confirmation of the Trinitarian doctrine.