I can't verify this online but a Catholic told me the churches all had a liturgy on how bad gay marriage is and handed out a flyer to remind all members specifically what the church's position was on it. AS IF a reminder was needed.
Now, call me opinionated, but sheesh. I get it, the bible condemns it, blahbety blah blah blah. So don't do it then if you don't want to. In fact, not only are you absolutely free to not do it yourself, you are even free to not conduct said ceremonies in your church. You could even excommunicate members who did it and you're legally entitled to do so.
Why the fark do they care who non-Catholics marry? This doesn't affect them in the least. It restricts no activities of the church, has zero impact on it.
Conservatives: Go ahead and be conservative and support the government butting out of people's personal lives.
That is all.