Gay marriage is bad because it will lead to polygamy! And we all know that polygamy is so obviously bad that its badness need not even be explained! Watch out! Polygamy's going to get you! And your civil society too!
Obviously she is not scaremongering. Why, she even brings up the fact that she might be accused of scaremongering to dismiss it out of hand. Polygamy! The real threat! Be afraid!
I might be channeling Fafblog just a wee bit today.