SG-1 usually had a very anti-theist message, as long as you group all gods together, but the writers went out of their way at least once to exempt the Christian God when the earthborn characters wondered if God might be a goa'uld: "Teal'c: I know of no Goa'uld capable of showing the necessary compassion or benevolence that I've read of in your bible."

The Christian God being a Goa'uld would break the theme anyway. They tended to divide up pantheons by species.