He didn't quit on "US". He quit because he has ethics and obviously Rogers doesn't. They were negotiating through August, with offers that were not what AA felt he deserved. Like how he did it or not, he had the team in a position to win and finally make the playoffs.
If Rogers felt that he hadn't done a good job, there should have been no negotiations. But in their usual idiotic manner, they were going to fire him, and then he turned the club around and now Ed Rogers had to try and save face. Just like he had done in the Duquette mess. Even with all that, they offer him a one year deal with an option.
So now, if you are in AA's position, you were the boss, and had done exactly what Rogers asked, and they are offering you an assistant GM job, with not even a long term contract. Big deal, you can walk away after a year. So that just makes AA look like some kind of whiny. ungrateful.
Sometimes, your own ethics take precedent and in AA's case, I say good for him. Sorry that he is leaving, and I will wait and see, but to all the Shapiro lovers, be careful what you wish for. His record, limited payroll or not, is mediocre. His drafting is unimpressive, and there are certainly enough Indian fans, cheering his departure. He was kicked upstairs because of his lousy on field record according to most reports.