Or so says one, very special kind of stupid, Ken Ham.
Ken doesn't believe in aliens because (paraphrasing) if aliens exist then, being non-human, they would lack the salvation available to "sons of Adam" (where the daughters come in, I don't know), and God wouldn't create a species in the Universe that lacked salvation.
Pointing out the idiocy in all of this nonsense is really like shooting fish in a barrel, or finding an idiot in Florida. So, further analysis is left to the reader as an exercise...
Creationist Ken Ham Says Aliens Will Go To Hell So Let's Stop Looking For Them
Even better, this is Ken's own site where he is truly an apologetic apologist!
But BE CAREFUL! If you Google "Ken Ham" and "NASA" together, you might just get the Astronaut Kenneth Ham, who, I presume, is a completely different person.