I think we agree exactly on your point B, or almost exactly. I would say that while Thorn is very good at justifying himself, things like the cursing of Larry Albo (whether it was an Imperio or something else, it was at least a public humiliation of the harshest kind) bring out his real quality. Actually, when it comes to that, his manipulation and use of his too-loyal sixteen-year-old son is even worse. It reminds me of what a really bad parent will do during a custody case, and it involves, not just mechanical manipulation from outside, but going there and making use of a boy's emotions and ill-judged loyalty to send him to his death for a purely physical advantage - manipulating him in person. What Thorn did to Maximilian, he did it face to face, and we have to remember that with all his honour and courage, Max was still only sixteen.

As for the rest, I have a suspicion that my problem may lie with JKR's own categories. It has always bothered me a bit that she should place so much emphasis on curses that, after all, only affect individuals, in the context of a society where people can be corrupted by the million. But I think we had better leave it there, because that would open a whole new can of worms.