The Roman Law (meaning the secular law of the Roman Empire) allowed only one legal wife per husband, although secondary liaisons with concubines, slaves, paramours, and prostitutes were common amongst the pagan Romans.
What clinched the deal for monogamy was that the Catholic Church accepted the Roman (secular) law of only one legal wife, and additionally insisted on fidelity of both the husband and the wife (no fornication, no adultery), as taught by Jesus and quite explicitly by Paul. Thus you had a "cementing" of monogamy in both secular and religious practice, set up by Roman Catholic law.
Rabbi Gershom (11th century AD) legislated mandatory monogamy for Western Jews, but this was only the formalization of what had been the actual practice amongst Western Jews for many centuries. I believe polygamy persisted longer amongst Eastern Jews, but it was not common, and was permitted only if the first wife was infertile, since the Jews strongly understood the purpose of marriage as procreative.
This argues my point exactly, although not completely. What your reference shows is that Jewish opinion has "evolved" (in left speak) to become less tolerant and less enlightened, and needs to be more inclusive.(again, in left speak) How would Jews argue against polygamy today? Obviously it isn't mandatory for Jewish person to be monogamous. Or for that matter, how will Protestants argue against this when Martin Luther endorsed bigamy?