Paul, as any stupid person, was unaware of the sentiments of others. Unaware of cultural norms, attitudes, and how he appeared.
For him, insulting his father was like standing on the podium. Hanging up on his mother was swatting a fly.
He had no idea of his wife’s culture. No inkling that showing such disrespect for his parents were sins she could not imagine.
To speak to his father with disrespect, in her hearing, to cut his mother’s call, made Kushi despise Paul and know that he might disparage her, her mother, her brother, the same way.
She knew he was the bottom of society when she married him, but she didn’t begin to appreciate that Paul had no morals, no respect, it was like marrying an ape.