So if the humans (and yes, they are HUMANS) in BSG drank acid and pissed laser beams, you wouldn't have a problem with that?
That would depend on how much sense it held within the value of the storyline. As Ford pointed out, that sort of example is particularly nonsensical as it is formulated to make no sense and have no perceivable value to a storyline. Anyways, at that point they wouldn't be humans, would they? Unless they called themselves humans, in which case that'd be not be corresponding to our biological definition of human but that of the storylines' universe (I dunno, like the Culture novels having humans able to change sex at will and soforth, justified by dint of their far future setting).
I repeat, the BSG universe is not completely hypothesised. It incorporates EARTH. Very specifically, by name. Their culture includes specific nontrivial details from Earth culture, like the naming of their colonies after the signs of the zodiac. There can't be any logical doubt that the Earth of BSG legend is the planet we're sitting on right now.
Having a planet named Earth, is seperate from having it as the original home of humanity; for one thing, AFAIK the BSG mythology so far states it as being simply a planet colonised by people from Kobol 2000 years ago.
Not to mention the use of signs of the Zodiac, Greek gods, etc has a symbolical as well as literal meaning. Like with ties; or do you think it'd be 'scientifically realistic' to expect fashion, in at least 2000 years time, had either retained the likes of ties, suits, etc (left modern/post modern earth), or convergently developed them (leaving Earth at a time when the Greek gods were still worshipped)?
This is not to say that Earth as a homeworld is the least likely explanation, etc, but to point out that the most important aspect is the dramatic one and the value an individual aspect has for the storyline; does it mean more to the viewer to reference the Arrow of Apollo, or the Arrow of Randomogodbloke? Earth has an inherent meaning as a homeworld, and the signs of the Zodiac have both celestical recognition value, and also a (tenuous?) connection to the foretelling/prophecy aspects of the storyline. If the show makes Earth have some other meaning than original evolutionary home of humans, I'm happy so long as it makes sense
within the story. Golden rule of storytelling.
And all that from a jokey throwaway comment about toasters. Phew.