The reason that I seem to be letting her off the hook is that she doesn't realize something very important about Michael: he's not really used to quiet yet. The Michael of 1985 needs the warm-up he talks about because until he leaves home, he's never been in a situation where it was quiet. What seems to be happening is that his mind won't let him buckle down and get to work until the normal, standard angry lecture about how he's a bad, selfish child who's stabbing his poor mother in her great big heart is delivered so that life is normal. He needs to have her screaming in rage to feel that life is okay because history teaches him that when she's silent, she's really angry.
Of course, now that he's gotten used to a life without people barging in and yelling at him about nothing at random intervals, he's got it into his head that he needs an alcove to protect him from his children.