The "joke" occurred shortly after Arianna made a "white men" "joke". I doubt he would have made his comment if she hadn't first made a similar comment that prompted that sort of kneejerk retort among two colleagues on familiar terms who are both at least two or more generations removed from the average tech worker. Arianna is 66 and Bonderman is 74.
https://youtu.be/b4q-WwXgYHU
That said, the comment was still inappropriate.