I'm sympathetic to it partly because I'm a bit like that myself. A while back, my mom sent a one line cheap shot at me that instantly sent me into total rage. So then I had to go deliberately (and irrationally) provoke a screaming match with her. I just couldn't let it go without first getting her as mad as I was. Plus, of course, family fights dirty.

And that last sentence is a lot more applicable to the fic than I had originally intended. :)

Yeah, the good/evil Snape thing was great conversation fodder for those two years. A random person had about a 50% chance of having read the books. More if I knew them. I worked a good number of people around from "He killed Dumbledore: he must be evil" to "Why, of course he's on the side of the light!"