alt Hacker News> suggesting that humans can't be that terrible
No, he's suggesting that children usually aren't that terrible. That a real scenario of ~50 unsupervised children (or adults), 99 out of 100 times, wouldn't play out that way. That something is possible does not mean it is the norm, and only those that can't grasp numbers (such as English majors) think otherwise. With such significant caveats, can one really say that the novel is about human nature in general?
You are pulling equally fictitious numbers out of your hat to defend your comfortable worldview, without even the benefit of extensive exposure to children as a schoolmaster, so how is your argument on any better level than Golding's?