This passage follows a paragraph about the difference between the filmmaking methods of Roman Polanski and John Cassavetes. Cassavetes was a great director, and also an actor. He played Mia/Rosemary's husband in "Rosemary's Baby." Polanski shot 30 or 40 takes, which bugged Cassavetes, who thought it "killed all the life in a scene."
One workday, while we were waiting to shoot, Roman was discoursing about the impossibility of long-term monogamy given the brevity of a man's sexual attraction to any woman. An impassioned John Cassavetes responded that Roman knew nothing about women, or relationships, and that he, John, was more attracted than ever to his wife, Gena Rowlands. Roman stared at him and blinked a few times, and for once had no reply."Rosemary's Baby" was made in 1968, the year Polanski married Sharon Tate (who was murdered the following year).
Here's a picture of Gena Rowlands and John Cassavetes in 1968:
And here's a picture of Roman Polanski and Sharon Tate, that same year:
Clearly, it was Cassavetes who understood marriage. It reminds me of the last thing Andre Gregory says in "My Dinner With Andre":