Stanley Donen's Saturn 3 is a half-crazy, occasionally-inspired mating of Frankenstein and 2001: A Space Odyssey...one that plays out between three humans and a giant robot against a high-tech, futuristic backdrop.
Taken on those simple terms, the film is enjoyable, literary, occasionally exciting, and consistently watchable, despite all the bad reviews you may recall from its theatrical release.
But when Hector and Benson arrive, they bring "the tree of knowledge" with them. On Earth, Adam would have feared being at the mercy of society, of the government, of his peers. Well, suddenly, in his perfect world, he is at the mercy of Hector, a psychotic who can control every aspect of his environment. Hector controls the air, the food supply, the temperature...everything. Adam is thus made slave to the very technology he has always feared and disdained, and that's a metaphor for the life he fled: one of regimented control where he was but a cog in the wheel. Perhaps that is the reason why Adam chooses to fight Hector to the death, because like Alex, he too has been ejected from paradise by the arrival of this interloper.