Christian by birth, if not belief...doesn’t work that way. Author must be Jewish.
It is very likely that the author of this piece is Jewish. Judaism is entirely based on race, themselves “the seed of Abraham.” The writer assumes Christianity to be race-based as his religion is.
The New Testament put great stress upon the fact that it is one’s faith - as opposed to one’s race - that makes him a Christian. One’s spiritual birth, not his physical birth. A concept hard for Nicodemus, a ruler of the Jews, to grasp, when Jesus told him he must be “born again.” His Jewish physical birth and race wouldn’t save him, in other words. John 3:1-5.