I think Dunne is very bitter about having his replacement pursued whilst still captaining the side.
It must be hard to know your employers are buying an improved version and the guy who will get the armband is playing alongside you at the same time, all the while you are expected to perform which he did.
However I believe Dunne wanted to go. Hughes has been pretty straight down the line regarding the club and transfers in his time here. He is on a knife edge with many fans and I dont think he would be so stupid to put one over a player many see as a legend.