Dude pulled a gun on him. If he had just recanted his testimony and THEN Dent punched him it would have shown his anger but that simply wasn't there. There's also no way having the coin showed he was angry. That's just revisionist. And people called him Two-Face because he was IAD and wouldn't overlook any misdeeds. It wasn't because he was mad.

Dent went from the supposed man of the people (even though we never really saw any people clamoring for him or him even really with the people at all) to renegade in no time flat.

I liked The Dark Knight but I don't think there's any way to argue that it shouldn't have been two movies. The Two-Face story line was horribly rushed and the ending didn't really make sense. After two boatloads people stood up to The Joker and showed they would risk their lives for what was right, they suddenly would up and lose their shit if the D.A. went crazy. Mind you, these people were already literally fleeing Gotham at the time so it's not like Dent was acting as much of a soothing presence. I really don't think Harvey Dent was anyone's white knight besides Bruce Wayne.

The film was almost all tell and no show. Better than Iron Man and very good, the film was still flawed and to fail to recognize those flaws is disingenuous IMO. You can argue that those things didn't bother you but they were definitely there.