On gay marriage

There's been another pother in the news, opposition to proposals to equalise gay marriage rights from religious spokespeople. This, in response, was on twitter:

When someone says ‘but the purpose of marriage is making children!’ we need to say: so you oppose infertile people late-middle-agers & OAPs marrying, do you?

This is quite a neat hermeneutic, I think, because the answer can only be 'of course not!' which in turn destablises the homophobic premise. But I doubt it would work that way, because the premise is not a rational one; it is an unconsidered 'ick!', a mental shudder and drawing away at the mere thought of men having sex with men, or women with women. What interests me is the extent to which this 'ick!' is akin to the 'ick!' some people feel at really old, wrinkly people having sex with other really old wrinkly people.