Just look at the marriage rate in the scandanvian countries that have legalized gay marriage. they have plummetted. at stake is the two-parent traditional family structure. widely recognized as the most beneficial for children.
So too have the fertility rates except of course among Muslim immigrants. They're having so many kids that Sweeden will have a Muslim majority by 2100. I rather doubt that when the Sharia replaces their current constitution, "gay marriages" will be allowed to continue to exist. However, the lists of "gay marriages" sure will allow the religious police to track down homosexuals.