This is not about what's best for kids. It's a political agenda by people who consider homosexuals sinful deviants. And the image of gays living in stable relationships, driving minivans, and caring for damaged children undercuts their cause and their moral superiority.
Actions tell us a lot more about what a person really believes than their words do. A person who really doesn't want gays to be executed or thrown in jail will join the call to decriminalize homosexuality, including putting pressure on governments to eliminate their laws against homosexuality which cause gays to be executed or put in prison. A person who opposes efforts to decriminalize homosexuality and then gives lame, unbelievable reasons for this, is not someone who genuinely doesn't want gays to be executed or thrown in jail. The words and actions don't match, and since actions are more reflective of what the person really believes, then the words must be treated as false.
The only truth in Federico Lombardi's words above is his statement that the Holy See is not alone — more specifically, not alone in supporting hate, violence, and bigotry against gays over basic human rights for gays. That, however, is hardly a defense or justification. If the best a person has to offer is to point out that they aren't the only ones who believe and act in this manner, then it's a tacit admission that they have no genuine logical, empirical, or moral arguments to offer in their defense. If they had good arguments, then the number of people who agreed with them would be irrelevant. Truth does not depend on being in the majority position.