Are you a parent? It seems to me you have an unrealistic picture of the power of mothers to shape children’s character.
What a child internalizes as normal is determined less by what parents tell them than by what they experience in the world. Before they even go to school, most of them have been exposed to thousands of hours of TV and other media. They observe interactions between males and females, and they experience the way they are treated by opposite-sex adults and peers.
Research suggests that most of the character-shaping influence of parents is limited to the first 8 years of life. After that, they are more influenced by peers and media.
Finally, a mother may tell her son that his father’s “shitty behavior” is abnormal, but when the son observes that papa not only gets away with being an asshole but gets what he wants by acting that way, which lesson (her words or his example) is going to be remembered?