As any parent will tell you, pregnancy and childbirth are only the beginning of all that is involved in raising a child. And those can be contracted out: adoption has always been possible, and modern technology gives us the option of surrogacy. Plenty of gay couples are raising kids, and have been doing so for years.
You're just trying to rationalize your prejudice by pretending it's about fertility.
You're overreacting. "> So, you think marriage shouldn't be available for straight people who are both infertile?" is, sadly, quite close to spite. Pointing out that gay couples raise children in significant numbers is a constructive argument, though this implicitly recognizes that marriage benefits are, at least partly, about procreation and child rearing.
You're just trying to rationalize your prejudice by pretending it's about fertility.