...and tell us there's no God.
That is why scientists like Carl Sagan so eagerly tell us there MUST be life on other planets, but it's a wish, there is no science to back up his claims.
So far, after decades of listening with radio telescopes, the skies have been totally silent.
Either aliens don't exist at all anywhere in the universe, or they are so far away their transmissions will never reach us.
And in either case, we will never have aliens visit us.
We are probably alone.
What if the aliens show up and simply say "There's a god - ours! Yours is just delusion."