He's just parsing the whole thing wrong. It's a pretty standard rhetorical device in everyday speech. Consider Passover, "why is this night different?" The ans

He's just parsing the whole thing wrong. It's a pretty standard rhetorical device in everyday speech. Consider Passover, "why is this night different?" The answer is not "because it's Passover". Your attention is being directed to why the night is different, why is it remembered, what does it commemorate, or why is it commemorated? The birth of Jesus, death, and resurrection are meaningful events at the core of Christianity, that's why they get holidays. Let me direct your attention to what happened on Christmas and why we celebrate it, Jesus was born. It's just not a strange construction in English or any language. Even if it was called Jesus's Birthday, what happened on that day? The Son of God was born. What happend on your birthday? Well, N years ago, you came out of mommy's tummy. I'm sure virtually every parent has said that to their child at some point. Only the autistic kids said "that's a tautology" (I can say that, I'm autistic)