I definitely see your point, but I do think it is a little different in this case, specifically for Counsell. It seems to be acknowledged that players' careers could end at any moment, so they need to get their money while they can. Yes, this could theoretically happen for a manager as well, but in Counsell's case, I think he is guaranteed to have a longer leash given his past success (whereas sometimes players' just fall off very quickly).
Given that there isn't much loyalty from players (which we have seen all too often in Milwaukee), the fact that Milwaukee had a manager who grew up rooting for the Brewers and was "one of us" as the commercial goes, I think it just stings that much more - more than if a player who just happened to be drafted here were to leave for more money. On top of that, to hear Craig's comments that the Cubs' job was his "dream"... it just feels like he's turning his back on Milwaukee when he knows firsthand what it's like for a small market team.
I'm not really disagreeing with you - if Craig wants to raise the floor of managers' salaries and get as much as he can, that's his right (and one he has definitely earned). But I think it's also the fans' right to feel slighted by this given his history and past comments about how special it is to manage the Brewers. As some said, I don't hate the guy... but I am definitely rooting against him now given the background and his choice.