"He can't be God"

When she said that, it really took away from the horror for me. Why couldn't the alien be god? Who says that all gods are benevolent? It's way scarier if the movie implied that we are the creations of some evil alien, and thus all doomed.

Even if it just hinted at that possibility would be scarier than an alien 'pretending' to be the Christian god Yahweh...