Are the marriages of infertile people generally inferior to marriages of fertile people?
Uh no. Your missing the point here. The point was to look back at how we were created to understand the purpose of why heterosexual sex is bonding in the first place. The why is for the good of the spouses, which in turn occurs for the purpose of the good of the children they are raising. Then we snap back into today and realize that sex is bonding because its also procreative. You do not have to have children for heterosexual sex to be bonding, but the reason its bonding is because its potentially child creating as well.
I think that there is nothing more bonding to me than raising a child with the person I love most: my wife.
I agree, although no marriage diminishes in value just because their objectively correctly ordered act did not beget children of no fault of their own. They would however miss out on the added bonding experience you are talking about in raising a child.
Gays could accomplish this through adoption.
Yes, but we don’t put children into homes for the good of the couple. Adoptions are child-centered i.e what is best for the child. We are not going to start allowing homosexual couples to adopt to promote gay monogamy… If its apparent they are not inherently monogamous relationships that already is enough of a reason to not allow them to adopt considering that kind of instability is bad for children.
Now you may argue that heterosexual marriages have a 50% divorce rate and that is instability too, but that instability is brought upon by the failings of the people in them, not because their relationships are inherently not as stable by virtue of their biology.