Monogamy is a cartel formed by males to reduce male vs. male competition for wives to more of a matter of quality than of quantity. The ability of a culture's males to cooperate with each other is correlated with the overall quality of life in that culture. But Becker doesn't seem familiar with that common argument.
The anti-polygamy argument to which Sailer refers is that social peace depends on monogamy. If it were not for monogamy, the competition among males for females would be so intense that there would be no social institutions. Men could not work with one another in corporations, associations, or any other joint ventures. Civil society would not exist.
This is a valid concern. I suspect that a major factor driving envy of the rich is a deep-seated male fear of losing the mating game. My hypothesis is that the irrational resentment that many men feel over the high pay of CEO's and others can be traced to a deep-seated fear that some other man will wind up with more than his share of mates, and the rest of us will be left with none.
The last thing we need is to turn that unconscious fear into something that is consciously justifiable.