Does same-sex marriage pose a threat to the fabric of society?

I just read a fascinating article written by the Mormon Church about why they are actively supporting California’s Proposition 8. While there are certain religious elements in this article that you may or may not agree with, I’m interested in what you think about the legal, political, and social arguments they express, and if you think these are important reasons for why we, as a society, should not redefine marriage to include same-sex couples.

http://newsroom.lds.org/ldsnewsroom/eng/commentary/the-divine-institution-of-marriage