Chapter 3: It Festers (Page 15)
He's reeeeally putting his back into p*ssing Ashley off. Ashley carries a lot of weight after what happened to her family and was constantly treated like garbage by the Alliance. It was a rather "Sins of the father" type deal. Maybe this is why she worked so hard to prove herself in her career. Well, Shepard clearly knows it's a hot button to push and will hopefully make her back off. All things being equal, he'd rather not have this conversation. He just wants to lie in his bed and pass out.
Good leadership says he needs to do this, though - he must listen to his crew when they have something to say.