It's interesting to note that regimes/ideologies that had Atheism as their official religion, were the premier mass murderers of all time. All other ideologies were complete pikers.
Well when "God" went out the window so did the value of a human life. If a person or group of persons are not useful to the state or challenged the state--they just had to go.
They were also in the 20th Century, with a much higher population to kill and much more efficient methods of killing and transportation. If the Muslims had this in the 700s, the slaughter of Christians in Europe would have been impressive. But then if the Christians had it, their slaughter of the pagans in that same century would have been equally impressive. Charlemagne would have been much more effective in Northern Europe if he'd had guns, bombs and artillery, and the Muslims would have had a great time.
You don't have to posit the actual existence of a supernatural being to explain that. Someone else made a similar assertion recently, and here was my response:
"[the feeling] that there is some God, is naturally inborn in all, and is fixed deep within, as it were in the very marrow. . . . From this we conclude that it is not a doctrine that must first be learned in school, but one of which each of us is master from his mother's womb and which nature itself permits no man to forget."
Ponder this classic observation:
"Primates often have trouble imagining a universe not run by an angry alpha male" -- AnonThat alone could be the "explanation" for the instinct to seek someone to obey/follow "which nature itself permits no man to forget" as you put it. It certainly fits in a great number of ways.It also explains why my dog worships me, and my cat doesn't. Creatures which have evolved a social structure revolving around an alpha-male (like dogs, as well as humans and other primates) will be "hardwired", instinctually, to expect and want a "ruler" to whom they give their allegiance and turn to for protection and permission.
Similarly, Arthur C. Clarke has suggested that man looks for a god because of the instincts which help us survive as a species having a long childhood. To keep kids from wandering off on their own too soon and getting eaten by the tigers beyond the safety of the tribe (and so on), humans, primates, and other animals with a long nurturing time have instincts which instill in the young feelings involving turning to your parents for protection and sustenance, looking up to them for guidance on how to live, fear of straying too far from them and being alone, respect for their position of power over you, etc. etc. etc. After growing up and/or leaving home, however, these instincts leave a yearning to continue to look up to some more powerful, protective nurturer/rule-giver. And a belief in a watching-over-me deity would fulfill this need for some people. Is it mere coincidence that so many gods are described in terms which are variations of "heavenly father", "our father who art in heaven", "god the father", etc.?
Further support for this potential explanation is seen in the results of studies such as: Vitz, P.C. (1999), "Faith of the Fatherless: The Psychology of Atheism". Vitz found that atheists tend more often than theists to have grown up with absent fathers (through death, divorce, etc.) or poor relationships with their fathers. If theism is an outgrowth of the childhood desire to have a parent to look up to and feel protected/guided by, then Vitz's findings make sense.
So Plantinga's simplistic argument -- which boils down to, "if we have a yearning for something greater than ourselves, then something greater than ourselves must necessarily exist", really doesn't hold water. There are many reasons why humans would have such a yearning entirely apart from Platinga's one possible explanation. His (and your) "that *must* be it!" mindset is not just simplistic, it's logically incorrect.