I've discussed my issues with the pigtail incident at length in a variety of threads on Hagrid; as it's not intended a joke, it didn't seem quite relevant here. It's hardly surprising that the Dursleys hate magic and everything associated with it at this point, is it? Of course, their hatred goes much further back, but with all the parallels, it seems reasonable that Petunia was (at least) once the victim of some terribly funny prank by MWPP -- or Lily (teacups and frog spawn, anyone?). Insert standard disclaimer that this doesn't in any way excuse their treatment of Harry, blah blah blah, still horrible, blah blah, responsible for their own actions, too.

I hope to get a chance to read the essay later, but quickly, what on earth is convenient about his disorientation? Just the fact that it gets Snape out of the room? Because I have a hard time seeing that whole incident as a plot device, when there are dozens of less nasty possibilities.