The Vatican has decided to stand against a non-binding UN resolution calling forth the nations of the world to decriminalize homosexuality, they feel that it is going to lead to the decline of heterosexual marriage and pressure for the states that do not accept same sex marriage equality to accept it. However I believe its positive because we are not leading homosexuals to marry the opposite sex in a relationship where the partner would deserve a heterosexual instead.
The Catholic church has led towards the support of the recently passed Proposition 8 in California and even though I have not actively been part of the church since my mother died in 1992, I would not want to be part of it again since they are not an inclusive church.
Problem is gay marriage is a nasty wedge issue that the Catholic church is trying to use to maintain its relevancy in being doctrinaire, but they are losing many people in the western world such as the United States and Western Europe. It is not about gay marriage in this resolution it is about ending the death penalty and jail for those arrested for being homosexual according to Franco Grillini a leading Italian gay activist.