Reading the letter from Arlene Sawicki, I wondered if she had ever heard of adoption.
The requirement of marriage partners to be of the opposite sex in order to procreate is unnecessary. Many same-sex couples adopt and create effective family units, complete with children. Many opposite-sex couples do the same.
Unfortunately, there are many children that are available for adoption and I think it benefits society more for them to be adopted, by same- or opposite-sex couples, than to not ever be adopted.
I also wonder if she has ever heard of married, opposite-sex couples who do not have children. I wonder how they feel reading her words, in effect saying that their marriages have less value. Many childless couples make wonderful aunts and uncles. They have the time to make their nieces and nephews a bigger part of their lives than they would be able to if they had children of their own. The parents benefit and, ultimately, so does society.
At one time, marriage was not only about procreation, it was also often a business deal. For the most part and in this country, that's no longer so.
All institutions and traditions evolve over time. Some go away. At one time, slavery was both legal and common, but I don't think we want to hold on to that institution.
Many same-sex couples want to enter into the institution of marriage, some of them want to have children. The result of more marriages and more families would be a benefit to our society. I believe it's time for the institution of marriage to evolve and expand to include same-sex couples.