Yeah, agree again. You are not really going against your W's wishes to say something to your dad. He was out of line IMO and I've personally told all my family to treat my W and my boys as they would without all this, it's not worth the knock on affect like you have experienced here.
Your W was venting, you listened, empaphised and agreed with her which maybe shocked her into backing down and telling you to let it lie. You can address this in a non confrontational way anyway and hear your dads side, but you must stick up for D11 IMO.
