The marital relationship between a man and a woman carries special advantages to society, and thus spouses have a special claim to public recognition and support.
The Church leadership seems to be of the opinion that economic and civil benefits must be dangled, carrot-like, to push people toward straight, traditional marriage; that without these benefits, we'd all be pairing up with folks whose parts match our own. Further, they must see a definite perk for The Church resulting from straight couples -- I assume the production of more Catholics.
This is wrong in so many ways.
Without financial incentive, was I going to go off and buddy up with Bruno rather than marrying Christine? No.
Due to financial incentives, is Bruno going to find himself a nice little lady rather than a man? No.
Is there a societal benefit to gay couples who are ready and willing to adopt and raise, in a stable, two parent home, family-less kids? Yes.
Do straight couples produce straight kids, and gay couples gay kids? No, otherwise there'd have been no homosexuals in centuries past, barring virgin births.
Should we be giving unto Caesar that which is his, and giving unto God that which is His, and keeping the two separate? Hell yes.
I'll never understand why The Church feels the need to stick their nose into gays' political and economic business, especially when they've already done such a bang up job of driving them out of the flock in the first place. If homosexuality is a sin, fine, label it as such and move on. If I recall correctly, Jesus repeatedly taught that the way we are to teach is through example, not through empty words, and certainly not by tending others' gardens while our own are glutted with weeds.