Unrealistic story, unrealistic expectations.
What. This makes no sense. Nobody acts like this. This is ridiculous. They're trying to get a message across, but they're doing it by depicting an unrealistic scenario. You can't do that; it doesn't work. It doesn't have a bad message; it just fails utterly at getting that message across.
Mama stubs her toe, the baby screams, and people aren't polite to each other at the breakfast table and call each other names. Everybody's mad. They get in fights. Mama takes the television away. Everybody's basically just hanging out and holding a grudge against each other, just glowering all day. Then Sister starts laughing at Mama for trying to read a magazine upside-down. Then instead of taking that as an insult, Mama starts laughing too and everybody else starts laughing like insane people, and they make up. Even the illustrations look like the Bears are forcing the laughter.
"But it's hard for folks who love each other to stay angry all day, especially if they really don't have anything to be angry about." No it's not! And when people are done being mad at each other, it usually takes a long time for them to get over themselves enough to accept, or offer, an apology. This type of deus ex machina resolution just irritates me.
The best part: "Who are you calling a slowpoke, you dumbhead!" Or, "'I wouldn't sit next to him if he were the last bear on earth!' said Sister. 'That goes double for me!' said Brother." What, if she was the last two bears on earth? What? I also appreciated when they were "looking daggers at each other" and the illustration actually had little daggers floating in the air between them. And how you could tell Sister is really upset because she is failing at staying within the lines as she's coloring in her coloring book. Furiously.