David is the game's most disturbing supporting character because he is competent, practical, effective, and genuinely capable of making people feel safe — all of which he deploys in service of something terrible. You do not make it to his position in the post-outbreak world by being good. He made it by being necessary to the people around him, by providing the organization and purpose that kept his group alive, at the cost of what that organization required.

The epigram applies to Joel too, which is the point. The game refuses to clean up the moral accounting by making the bad people obviously monstrous. David is what thriving looks like in a particular form.