On the subject of corrupt-vs-build, Tolkien's contemporary CS Lewis had some good bits in The Screwtape Letters, in which a senior devil is advising a junior on the corruption of his charge. (I don't think one needs to be Christian to pick out its insightful bits on the human condition.)

> Well, I am afraid it is no good trying to make him brave. Our research department has not yet discovered (though success is hourly expected) how to produce any virtue. This is a serious handicap. To be greatly and effectively wicked a man needs some virtue. What would Attila have been without his courage, or Shylock without self-denial as regards the flesh? But as we cannot supply these qualities ourselves, we can only use them as supplied by the Enemy—and this means leaving Him a kind of foothold in those men whom, otherwise, we have made most securely our own. A very unsatisfactory arrangement, but, I trust, we shall one day learn to do better.

> Hatred we can manage. The tension of human nerves during noise, danger, and fatigue, makes them prone to any violent emotion and it is only a question of guiding this susceptibility into the right channels. If conscience resists, muddle him. Let him say that he feels hatred not on his own behalf but on that of the women and children, and that a Christian is told to forgive his own, not other people’s enemies. In other words let him consider himself sufficiently identified with the women and children to feel hatred on their behalf, but not sufficiently identified to regard their enemies as his own and therefore proper objects of forgiveness.