To me, there were two elements of Harry's behavior that stood out and are distinct from one another. The first was Harry's initial attack against Rudolph. I would expect that under the same or similar circumstances; not every person, but a large percentage of population would react with a similar amount of rage and violence; if they were capable of physically delivering it. What was more disturbing was how long Harry held onto that rage and that he seemed to be reveling in it. I think a much smaller percentage of the population would go that far, but I have no doubt some people would. When Harry lets his anger control him you understand why the White Council is afraid of him. So I partially agree with you. Harry, absolutely needs to address his anger issue before he goes too far one day and can't come back. However, I don't think he's a lost cause.
One question, but if you don't care to answer it, I understand. You said you've felt that kind of rage, did you stop yourself in the end or did someone else prevent you from causing further damage?
But back to the story, you also say that it is disturbing that it took so much and it so long before Harry could be stopped. I think that is where the mantle comes in, it lives for rape and violence, it revels in it, it makes whoever holds it, a monster if not tightly controlled. Since Changes Harry has
fought those effects, not always successfully, but more than most, because he understands both the benefits it brings in a fight, and the draw backs because it is mindless and stimulates the strictly mindless animal parts of the brain. His reaction to Murphy's murder was a normal human one, but then it triggered the mantle, that took over and it was no longer human, it was no longer Harry. It took an archangel to stop him, a burn from a Holy Sword to cut through his very real pain, and the mantle's power to bring him back to being just Harry once more. The fact that he could be brought back, feels real remorse for losing it and continues to feel shame when he thinks of that burn says he still is the good man he always was. Both Butters and Sanya understand that, the archangel in charge of the Sword of Hope also understands that, that is why Harry merely got a nasty burn to remind him of his danger and very near fall, It didn't cut his arm off.