Gay marriage is either a right or nonsense depending on your view as to what is the purpose of marriage.
The best way to bring new life into this world and raise this life to become functional adults is with a mother and a father in a supportive relationship. This is by far the best predictor of success. It is the rationale behind the significant biological, cultural, and legal advantages of a married couple.
We should be encouraging young couples to have children within a long-term committed relationship. Gay marriage only distracts from this goal.
Let us accept gays for who they are and their accomplishments, and not ask them to pretend to be something they are not for social acceptance.