I've pointed out before and Thursday agrees: average males benefit from monogamy more than anyone else. Despite widespread bravado, middling men would be hurt the most by polygamy. Regarding the "sexual revolution":
Beta males are the one's getting the biggest shaft here. They are forced to compete with Alpha males, meaning that they are often left out of the mating game as the Alphas monopolize more than one woman at a time. Should they actually find someone to mate with, chances are it will be with one of the Alpha's leftovers. More than just the psychological unpleasantness of having other men "break in" their woman, this means that Betas are often left to deal with the bitterness towards men that repeatedly being pumped and dumped by Alphas often bequeaths to women. Not to mention having to measure up unfavorably to the Alpha's sexual performance, and fact that the women is unlikely to bond as strongly with him after having fallen in love with an Alpha.
Alpha males have, of course, made out like bandits. They frequently get the benefit of multiple consecutive or concurrent relationships with various women. If they want to settle down, they rarely have much difficulty in finding a long term mate. Of course, if they try to hang on too long, they do risk ending up alone or with some lesser female in the end, but if they are smart they can end up with the benefits of both easy sex and commitment.
It took centuries for beta males to build a society that valued monogamy and marital fidelity and punished promiscuity, and the end result was quite beneficial for most women at the same time. Unfortunately the alpha males formed a coalition with the beta females to overthrow the order in the name of sexual freedom, and it's the alpha males who reaped the biggest benefits.