It depends on how you look at it. What he's referring to is the Long Decade, a period from 1945-1962, which some sociologists see as an important transitional point in the traditions of marriage. Indeed, when homophobes appeal to "traditional" marriage, they're referring to the Long Decade, not the longstanding traditions that started coming apart in the nineteenth and twentieth centuries when the purpose of marriage changed drastically.
I recommend Stephanie Coontz's Marriage, A History: From Obedience to Intimacy, or How Love Conquered Marriage (New York: Viking, 2005).
Monogamy has often been subsumed under the rubric of "sex outside of marriage". But Western society's focus on sex outside of marriage, for centuries, looked primarily at women. Part of the reason for this was how society looked at women in general. Blackstone, in 1765, affirmed the English common-law principle in marriage, "the very being or legal existence of the woman is suspended" (qtd. in Coontz, 186). This principle carried on into the twentieth century, even in the United States. In England, this resulted in an 1889 court order that a woman owed her husband "restitution of conjugal rights". Comparatively, very few of the laws of religious or civil society focused on the men.
True, one can argue that Savage's statement is certainly open to specific details and questions that might seem to contradict it, but thematically speaking, he is correct.
