Stalin, Pol Pot and Hitler were not followers of any monotheistic religion. They wanted a humanistic, areligious, scientific organization of society.
Hmm, no.
The nazis ripped down Christian ideas and were resurrecting pagan ideas in their place, much akin to druidics. They worshipped the "blood" or "lineage", which is a form of ancentral worship. Primitive? Yes. A religion? Certainly. They had the mythology part covered as well - the ideas of ancient aryan homeland producing all the wisdom in a sea of subhuman barbarians. They even had a "bible" that they printed on cattle hides, bound in steel, and entombed in a concrete sarcophagus to be opened after 1000 years. They had their Pontifex Maximus (Hitler) to preside over holy rituals. They had clerics and monks (propagandists, SS-men), warrior-monks (Waffen-SS), even a form of templar (SS-MDs) to protect their holy grail (pure aryan blood) from corruption (propagation of the defective, misalliance with the untermenschen) by purges (castration of "idiots" and deathcamps for the untermensch). They had their religious rallies - torch marches - druidic in symbolics and certainly mystic in intent, meaning, and effect - a form of group communion with their deity ("the pure blood"). They even had their own version of the Second Coming - the production of Nietzschean supermen - which they were striving to foment by selective breeding to purify the contaminated aryan blood. Finally, they were highly motivated in their atrocities exactly by that religious faith, rather than by "scientific" ideas.
Similar things can be found with commies as well. Their worship was one of the Big Communist Kumbaya, which is essentially a collectivist perverted humanism. They had their highpriest (GenSec), temples (Party Houses), preachers (PolitRuk), bibles (Das Kapital, gensec writings) and enforcers (Commisars, NKVD/KGB) as well as the religious zeal and intolerance of true believers. As far as science goes, they really stuck their heels with genetics because it was inconsistent with their Marxist dogma that environment and not lineage determines properties. If they were "scientifically motivated", they would not have rejected such a major advance as genetics.
Taking into account that the first thing Pol Pot did was slaughter doctors, scientists, teachers, essentially anybody with highschool education or above, your claim above cannot be taken seriously.
Interpreting evidence to fit the theory because of an unshakeable belief the theory itself must be true, rather than re-questioning the theory as new evidence presents itself is worship of the theory.
Provide objective evidence against current scientific understanding, and we will gladly consider it.
There are a lot of people who cling religiously to "scientific" ideas because they can't face uncertainty either. They accept anything someone with a doctorate tells them as ardently as a 10th Century peasant trusted his priest.
If they cannot face uncertainty, they would not like what their PhD tells them, which is natural laws (certain) plus probability (inherently uncertain, a toss of the dice). In fact, I would argue that religion is far more "rigid/certain" than science exactly because of it. Omniscience, omnipotence, omnipresence, etc...