My mom takes everything personally so she started commenting that he didn't like her (how could I say it's not you mom, it's me).
STRONGLY DISAGREE
It is not YOU it is HIM. He is depressed and the feelings are not inside of him. He does not have LOVE for anyone right now. The depression is clouding his view of the world. He is trying to run away from it and figure out what will make him feel better. That of course includes YOU and anything associated with YOU. No matter what you might have done it would not have changed his depression.
As far as your MOM goes, yes it was better left unsaid. However the poor communication continues between you and your parents. Kind of helps with his justifications, typical I guess. Well they know us better than anyone else and use that against us, to somehow make us think it is our fault.
It is not going to bring him out of his depression one way or the other.