That is strange that you referenced the Georgia Guidestones. When I first read the article that is exactly what came to my mind.
Enough mystery surrounds their emplacement (for whom?) that it would appeal to folks who are 'into' the occult and wierdness, and those are the sort of people I'd think might be most likely to embrace some sort of philosophy which would entail the death of huge numbers of (other, of course) humans.
People who lack some strong moral compass or means of guidance are easily prey to arguments for eugenics programs of all sorts.