I just don't get it.
Why not simply say yes, OK. A historical person named Jesus was born in a manger and (religious) shepherds did believe they heard what they (mistakenly) thought were something called 'angels' and His family did flee to Egypt for fear of a Middle Eastern despot who may or may not have committed atrocities against his own citizens etc etc.
You're not compromising your atheism by accepting a secular history of Jesus.
No Christian apologist to my knowledge has ever claimed that Jesus' (secular) historicity necessarily compels belief in miracles as the only explanation for the events reported in that history.
I quite agree that we could easily theorize that there was an actual Jewish preacher/teacher in that ancient day, who was the bit of grit around whom all the miraculous myths and legends of the Christian faith grew, like a pearl in an oyster. Historicism is in no way the same thing as Christianity.
Thing is, that theory just doesn't seem to fit all the texts we have, and which we do
not have, as well as the theory that Jesus Christ began as a dying-and-rising savior god springing from the interactions of Judaism and paganism, and from the terrible events of the Jewish Wars.
Sure, there could have been a man who inspired the myth. I think that Buddhism began that way. But in the case of Christianity, I think the myth created the man.