My main problem with those who hold the theory of intelligent alien lifeforms is that, being intelligent, they would be capable of sin, and being the subjects of sin, they would be in need of the Blood of the Redeemer. Essentially, maintaining these extra-terrestrial beings to exist is essentially affirming that there are intelligent beings (not angels) who are not corrupted by sin and potentially not in need of redemption. This is heretical on the face of it.