So what your saying mooeypoo, first of all that all religious belief is bunk? Because there is no evidence of a any kind of god, it's for simpletons. All things without corroborating factual evidence are just bunk and easily dismissed, as bunk.
There may not be factual evidence, but there is speculative evidence, pictures, drawings, ancient texts about visitors from the sky, from most ancient civilizations, the Maharataba for one, is a compelling read. Speculative evidence, or could I say "Theory"....? And who is to say this evidence is not factual? You? You going to tell me that the ancient peoples were idiots, simpletons, or just storytellers? Now they may have been all that, but again, they may have been describing visitations from alien life forms....Do you know for sure which it is....?
So all the show is putting this 'evidence' out there, but your saying it's not 'rational' to create 'theories' on speculative evidence....Science is full of 'theories'....
The four bullets that you described....yes if no. 1 is true that doesn't make 2 & 3 true, sure, but on the other side of the coin, it could....the theory IS debatable, the corroborating evidence is mentioned above, ie. texts, drawings, descriptions of what they witnessed, etc.
Also, I don't think I've ever heard that the aliens built monuments to themselves, It's a general 'theory' that the peoples of earth built the monuments to them, in anticipation of they're triumphant return....