Earlier quoted context omitted.
Maybe it's because that the religion is one of the most important factors which formed these alliances and adversaries throughout the history. Without these cultural and religious layers, what remains is same for everyone. A human body.
Sure, you are correct. But that also means Jews/Christians have a very rocky road together. Technically, "Christians" performed the Holocaust, for starters. It begs a question - when you add in Islam, why do Christians and Jews suddenly become political allies?
It's important to note that we throw around terms like The Muslims as though all Muslims and Christians, etc have the same beliefs and agenda, and that's clearly not the case.