Sincere as these people are, I'm forced to disagree with them.
A reading of Jesus' teaching in the gospels, along with the preaching of the primitive church, leads me to the conclusion that Christianity's core message is the kingdom of God. The Christmas story is about Messianic hopes, not metaphysical christology.
Consider the Song of Mary in Luke's gospel:
"He has performed mighty deeds with his arm;This is the same message that blazed forth from the Hebrew prophets. A great successor to David would come and take the throne, ruling with perfect justice. Peace and goodwill were destined to reign on earth. The knowledge of the Lord would fill the world from the rising of the sun, to its setting.
he has scattered those who are proud in their inmost thoughts.
He has brought down rulers from their thrones
but has lifted up the humble.
He has filled the hungry with good things
but has sent the rich away empty.
He has helped his servant Israel,
remembering to be merciful
to Abraham and his descendants forever,
even as he said to our fathers."
Angels heralded the beginning of it all in Bethlehem. The realm of God had penetrated the human realm in a new way, never before seen.
We're called to continue what began on that day. The incarnation is not a theological abstraction designed to satisfy speculation about Christ's ultimate identity. It's not a dogma that we merely file away under the "orthodox" tab. It's a reality that we fulfill ourselves in this world.
When we love our neighbors, forgive without end, become like little children and live irreproachable lives, we bring heaven down to earth. The kingdom of God comes with power.
And our work continues. As long as "peace on earth" is absent from any corner of our globe, we Christians have a lot of incarnational work to do.