I understand the patron's discomfort, although to see it in a different perspective, if the "offending woman" was Greek, her social and etiquette norms might have been different than the "norm" here. I have seen plenty of babies being changed in public places in more ethnic places, and I have seen Indian women on Devon Avenue openly breast-feeding without covering themselves like most "Western" women do.
I am not suggesting judging the situation in a right or wrong ideology - although I would suggest that rather than adding fire to the situation, the patron could have approached the management to take care of the situation at the onset, particularly since the patron stated they knew the owners for a very long time.
I don't feel it is appropriate for a patron to reciprocate a "rudeness" with another patron in a restaurant.
Leave it to the management to take care of it.