Mainstream scientists have been speculating about other-than-earthly intelligence for decades.
Supernatural agents that exert natural effects are perfectly valid objects of scientific inquiry.
The most valuable aspect of his case is the stimulus it provides to the question, “If non-human intelligences exist, how would we detect them?”
The evidence seems pretty light, at least compared to what we normally expect for a design inference.
Loeb’s argument represents the most salient example of risky intelligent design reasoning in mainstream science.