You know, that's how I imagined it when I read it too--I thought it was just funny that he was described as being so hated but it turned out he wasn't hated in an Umbridge-way, but just because he made all the kids feel stupid by having no patience for their teenaged angst and snivvely kid problems.

Heh, no wonder the quintissentially Gryffindor Sirius thought that Phileas Nigellus would be so hated! If Harry's anything to go by, the worst thing you could ever do to a Gryffindor would be to laugh at them and expose their "chivalry" and "bravery" as the poses and pretensions they really are.

That said, the patent disbelief that affected Phileas Nigellus after he heard of Sirius' death was immensely touching... especially that description of him leaving Dumbledore's office to call for Sirius through portraits in the Black house. That was more affecting and real than any amount of shrieking Harry did-- and was possibly the most human moment any Slytherin has gotten so far in the books. Though as is typical, the Slytherin in question wasn't even a living or real one!

"But dammit, man. He was in my club!"

Heeee! But hey, it's hard not to like a guy who gave you so much business!