I think that he lost all right to be called a hero when he Crucio'd Amycus. He'd been annoyingly passive up till then, but...the way I figure it, a grey character or an anti-hero could develop noble qualities or feel remorse for his/her actions and become heroic. By the same token, if the traditional heroic character does something vicious or wrong that the villains have been condemned for doing, does it with all the enthusiasm of the bad guys and feels no remorse, regret, horror, etc. afterwards...

...then, to my way of thinking, the heroic character is not a hero anymore, and isn't going to be ever again.

Harry has had so many "not a hero" moments that I can't count them. Trying to Crucio Bellatrix. Using the mourning of a supposed friend to get Slughorn's memory--now that was completely vile. Intimidating Sluggy into giving him that memory after Hagrid passed out drunk. Attacking Snape with a fatal spell when he knew there were a thousand other spells that would be more likely to capture the man. Trying to kill Snape with Avada Kedavra. His inability to think or act. This scene. I'm sure people can think of others.

Harry isn't a hero, save in the eyes of his creator. It's a shame that she doesn't realize it. I don't like the fact that a generation is now thinking that passivity, lack of thought and casual cruelty are heroic traits.