I understand the disappointment, but not the anger (and I'm not trying to sanctimonious). Assistant coaching is a very unstable career and I don't blame any one of these guys for looking out for themselves. He has ties to the Wisconsin program, so it fits.
But it is disappointing, he seems to be a good recruiter.
As for the slap at Kill being a "B Squad" coach, I doubt someone in Hammock's position would use a term like that. Liking one's boss can often be a luxury and if Hammock didn't like Kill or O'Brien, that's too bad. It's his job to do his job. Too bad he couldn't do it here, but I don't buy the "discomfort" argument and if that is why he left, good riddance.