Lord of the Flies is a fine horror/adventure book, but its central premise--that people will revert to barbarism and human sacrifice--is false and dumb and sucks ****.
I think in Golding's case he's projecting his own bleak view of humanity on to a bunch of kids he made up, and appealing to the internalized authority of Imperial England who until very recently spent centuries traveling around the globe using violence to "enlighten" various people they determined to be "savages". It is a parent beating a child "for their own good"--ultimately an appeal to authoritarianism.
Also, in 1965 a bunch of actual boarding-school kids were actual castaways on an uninhabited South Pacific island and they lived there for months and didnt murder one another and in fact functioned quite cooperatively for 15 months.
en.m.wikipedia.org