That opinion is based on the nauseating self-pity, rock-ribbed Neanderthal sexism, revolting refusal to sympathize with others and blank-eyed stupidity that define Michael T Patterson, Purveyor of Overwrought Abuse Porn and can best be summarized by his wailing about how his parents could be so horribly cruel as to subject him, Michael Patterson, to the mildest bit of ridicule. As it was when Mike pissed and moaned that Elly was embarrassing him by protesting the possible demolition of the old town hall, his need to do the teasing and not be teased himself takes priority over all other concerns.
As an example, he can't possibly be troubled wondering why Elly is so ambivalent about the whole thing. After all, the idiot would have thought that women existed to fall down at his feet and serve his worthless, lazy ass even if John had actively discouraged such thinking so we can't expect him to change because his mother is pregnant any more than we can expect the toxic waste dump in the chinos to relate to Liz's fear that she'll be ignored because there's a new baby in town.
That would require him to do something he fears and hates because of his baffling belief that empathy means enslavement: being any sort of emotional support to Sistwirp. Instead of bonding, he all but told her that it was God's way of balancing the scales for hurting him by not being a kid brother he could play with instead of a gross, useless girl.
What makes this all the more ridiculous is when he was busy ignoring April during his occupation of the Pattermanse and crying crocodile tears while his imbecile parents were running around in circles squealing about how she wanted him and his family to die in the gutter so she could sit in her room, look up scary information and listen to headache music, the sordid chunk of flotsam dared call her his little buddy. He went into life feeling like the only reason she came into the world was to spoil his day and now that she's away from the fetid stain on the map that is Milborough for good, he howls with confusion as to why.