You persist in your twisted way of equating marriage with procreation. Given that you've repeatedly refused to consider adoption or fostering as legitimate means of starting a family, and with artificial insemination still a very marginal method of getting pregnant, you ARE in effect equating marriage with Fucking For Children -- i.e, talking only about the sex. (What; I never said you were talking only about the _gay_ sex, now did I?)
All that's missing is prescribing the missionary position as the only Pure way of doing it, and your standpoint would be totally indistinguishable from that of the most brimstone-and-sulphur-reeking fundamentalist Bible-thumper imaginable. So, eh... Which positions are OK to qualify for marriage, in your book?
HTH!