The ad is just part of the sodomite war on what is left of our Christian culture. Male sodomites don’t want children any more than they care much about “gay” marriage as an institution for themselves. The ones who want these things are primarily lesbians. The males have generally gone along, without much enthusiasm, as culture warriors.
McDonald is an atheist/agnostic (made clear in other writings), and her argument rests on claims about evolution and what is best for the child. As she should know, you can’t derive an “ought” from an “is” (David Hume). Consequently, her argument can always be dismissed by the great liberal “So what?” if they tire of trying to convince people of the lie that the sodomite burlesque of marriage is “just as good for children” as the “repressive, patriarchal, heterosexist, blah, blah” model that they seek to eliminate.
But the central point is that in a postmodern worldview, liberals have no reason to “privilege” the interests of children above their own - even if they were to concede that in some sense traditional marriage is better for children. Even if a metaphysical naturalist like McDonald were to effectively refute postmodernism (not all that hard to do), she still faces the the Humean dilemma, for there is no solution to the is/ought problem within metaphysical naturalism (which may have inadvertently been Hume’s deeper point). Consequently, for a metaphysical naturalist moral discussions are ultimately just chit-chat about personal preferences, and any conventional morality is just an artifact of a successful sales job.
It is this moral hollowness of metaphysical naturalism - which is associated with “modernism” - that the left has so effectively exploited to destroy our culture. A Christian culture cannot be defended within the context of a materialistic metaphysics.
I guess that the religious gay couples want to see same sex marriage legalized, otherwise God will see them “living together in sin”.