Christians...Why do you say Allah is a moon God?

Christians think that their GOD is the only living God and revealed itself in NT. Even OT God isn't considered God by Christians since god wasn't a Trinity in OT. They refuse to acknowledge that God in Islam is the God of Abraham because Allah isn't Trinity. Allah is one without partners and a son. Christians believe that God has a kid who was sent on Earth to be scapegoated so one day people like Lady Gaga might call themselves devout and religious people Astaghfirullah.