Procreation Imperative isn't needed

I wrote a while back about the Procreation Imperative, the idea that unless you are in a religious order that demands celibacy, you must get married and you must produce children. Now comes a report that the USA birthrate in 2006 achieved replacement rate, something unique among industrialized nations (where the birthrate is much lower) and something American hasn't done since sometime around 1965 at the end of the Baby Boom. Note that this rise in the birthrate comes after gay marriage in Massachusetts and after civil unions in a few other states. Gay marriage is not going to make anyone stop having kids who wants them. Add in immigration and the country's population continues to increase (haven't heard much about overpopulation lately, have we?). So why is the Right in such a stew over procreation? Might it be because there aren't enough white babies being born to counteract all the brown babies that are immigrating? Surely it isn't racism.