I'd just ask him why he's being disrespectful to her. No matter the situation he shouldn't disrespect her, if he's blaming her for the divorce I'd probably say something about it's complicated and will take some time.
Me 38 Her 38 Daughter 7 Married 11 Together 16 BD 3/21/14 Moved out 3/8/15 D final 3/11/15