This would not "mess up" even a single Christian.
The existence of life on other planets would do nothing to disprove the Bible, and Christians understand that all things are possible with God.
However, I can see how this WOULD "mess up" a lot of secular humanists, because they can't conceive of anything greater than humanity.
Steven Spielberg says his new movie, Disclosure Day, about aliens will have Christians and people of faith second-guessing their own religion.
Spielberg says the movie will take the position of the Church.
"Is God our God only on this planet, or is God a God for every system where there's civilization?"
"That would mess up a lot of people."