Some believe in Jesus, sight unseen, all through witnesses long since dead. How is this different?
"Now faith is the substance of things hoped for, the evidence of things not seen."
I've never heard anyone equate their faith in Christ to a belief in space aliens.
Seems to me it is not different. No one I know of has seen Jesus or Alien critters. Not for at least 1000 years.
A suggestion from someone much more intelligent than I was, "You want to see an alien? Look in the mirror". We may be the children of another sun.
The truth is stranger when you think.