Wow - mom seems like a tough cookie, but she is your mom and I'm sure she loves you. Still, if she thinks that her words will eventually get to you, she'll keep at it.
Honoring and respecting parents is really important, but there is a limit. They shouldn't ever ask you to disrespect another or do other sins/"badness".
If you want an end to her berating him - I think if you tell her that you will not be a part of the conversation, and leave, and she continues then leave again after letting her know why. If you have to do it 7,000 times, it will eventually (partly?) sink in for this topic. Only she can change herself, but just as we've read to do with a spouse, setting boundaries and then acting on them (painfully, repeatedly) can get the message across. Mrs A made a point to consider - telling H that you stood up for him shows him that you are committed. It also tells him that if he does screw up, you have the strength to follow through a little more than you already have.
BTW, I checked my dictionary, and there was a woman's picture in it... (kidding~)
