Same-sex Marriages

I came across this interesting article in Catholic World News (CWN) regarding same-sex marriages. As more countries and states legalise same-sex marriages, what if one day Singapore faces this option? How should you as a Catholic argue against the legal recognition of same sex marriages?

The same-sex marriage proposal is a scam. Here's why.

A) Eric is married to Kate. Their marriage provides the state with many significant benefits.

1) They produce in their children the next generation of citizens.

2) They provide a very great part of the education and socialization of their children, teaching them to communicate, to cooperate with others, to do their fair share of the common toil, to restrain their appetites in service of a common good. Most of the values that incline citizens to contribute to society (and to act so as to stay out of jail) are learned in the home and inculcated and reinforced by parents and siblings.

3) When the young behave in harmful ways, most of the needed disciplinary correction will be meted out by their families and the more stable the family, the more effective the correction is likely to be.

4) Eric and Kate are interested in the welfare not only of their children but of their children's children, and consequently have a vested interest in the long-term prosperity of the state (and neighbourhood), and inculcate the same sense of responsibility in their children.

The state can, in unusual circumstances, provide or attempt to provide benefits 2, 3, and 4. The state will almost never succeed in providing them as well as an average family, and the expense involved will always be grotesquely disproportionate to the effect, as compared to the same benefit provided in the context of married family life. Because Eric and Kate make sacrifices in order to stay married and raise a family (sacrifices involving career choices, education and health expenditures, etc.), the state traditionally acknowledges the benefits provided by partially compensating Eric and Kate in legally "privileging" their marriage: recognizing the marriage as a civil reality, making it difficult to dissolve, penalizing polygamy (whether serial or concurrent), protecting property by inheritance law, and so forth.

B) Greg and Charlie graduated from college together and both have entry-level jobs in business. They are friends, and room together to cut expenses by sharing rent and utilities, and because they enjoy each other's company. Their main interests are in providing economic prosperity and security for themselves and in pursuing their own amusement. Their conjunction, in and of itself, provides no benefit whatever to the common good; each individually makes contributions as a working and tax-paying citizen, but each would make the same contribution if he lived alone.

C) Dave and Jason live in the apartment below Greg and Charlie. They graduated from college together and both have entry-level jobs in business. Their main interests are in providing economic prosperity and security for themselves and in pursuing their own amusement. Each individually makes contributions as a working and tax-paying citizen, but each would make the same contribution if he lived alone. Dave regularly sodomizes Jason. The principal reason they share the domicile is to facilitate this conjunction.

Question: what good does the conjunction of Dave and Jason provide the state that the conjunction of Greg and Charlie does not? How do we, their fellow citizens, benefit from their partnership? In what sense is their relationship productive of the common good such that the state would want to assimilate it to the marriage of Eric and Kate? Keeping in the mind that the recreative appetites of Greg and Charlie were not specified and so may be heterosexual or homosexual or some combination thereof what is it that we, the citizenry, stand to gain by the fact that Jason is sodomized by his roommate?

Or, if this picture is seen as too reductionist, what public, civilly verifiable fact about Dave and Jason's relationship makes it a "same-sex partnership" in a way that distinguishes it from the same-sex co-habitation and friendship of Greg and Charlie? What, in short, is the state imagined to be rewarding in granting civil recognition to their partnership?

Edit: Link provided.