My mother never saw the irony in calling me a son-of-a-bitch.

The line hinges on a dark, self-deprecating joke: the insult “son-of-a-bitch” is typically aimed at a man by disparaging his mother, yet Nicholson frames it as something his mother herself would say—thereby collapsing the usual logic of the slur. The “irony” is that if a mother uses the phrase about her own child, she is (in the insult’s crude terms) implicating herself. Read more broadly, it plays on Nicholson’s public persona—acerbic, profane, and wryly reflective—using taboo language to expose how casually people deploy insults without thinking through their meanings. It also suggests a family dynamic where sharp language is normalized, turning offense into humor.