So consider gays a benign exception too.
That covers infertility, but what about post-menopausal women? We know they can't have children. It's normal, not a failure or an exception. How many older women get married every day, yet you seem completely unconcerned with that?
Uh, no, people who have no intention of forming a family get married every day. Some dont' want to, many cannot (like post-menopausal women). And, as you have been reminded, gay couples can indeed start families through adoption, artifical insemination, or by caring for children they had from previous heterosexual marriages.
Society already routinely accepts the marriage of people who can't have children, and who we know can't have children (post-menopausal women). So saying that marriage is for children is a completely load of bull****. So everyone stop saying that, or else advocate banning marriage for old ladies. You gonna do that again, Jerry?