Nope, that's natural, and you can't help it.

I find a better strategy is to argue: "Well, of course I agree with you -" [always say this and nod, it will make them think that what you're about to say is something they already thought of] "-and of course any good and stable couple is going to ensure that they have a role-model of a different gender. Gay or straight, it don't matter - gays who prevent the kid from having an Aunt/Uncle figure are as bad as single mothers who hate all men. But C'mon man, honestly, how many gay guys do you know without a platonic girlfriend?"