It is a recognised logical fallacy, Toni Lavis. The Appeal to Tradition: http://en.wikipedia.org/wiki/Appeal_to_tradition

There's another one to add to the Slippery Slope and the Appeal to Nature.

Aj,
One doesn't have to be a theist to understand that the basic building block of society is the family and that heterosexual marriage is the long standing convention in all societies which currently exist or have existed in the past, even atheistic ones like the USSR and Red China. Same sex marriage only appeared in public discourse and political platforms about twelve years ago, before that not even Gays mentioned it and Gay activism has never been about equality, it's always been about recognition of alternative lifestyles and special treatment for special groups.
The response to the NZ prank is revealing because it shows that re defining marriage in that country has opened it to this kind of ridicule and created a new form of discrimination? Why shouldn't two heterosexual people of the same gender be allowed to be married and be treated in exactly the same way as other same sex couples?
Furthermore and taking a point from that article since when has marriage had anything to do with love? That's just another talking point invented in the last few years, what, are Gays suddenly going all Mills and Boon on us? I think even the fat spinsters who do read romance novels and watch romantic videos understand that it's all a fiction. Marriage is about a partnership between a man and a woman wherein she allows him to sire her offspring in exchange for a share of his resources, shelter and his protection, it's a bargain made between males and females in order that they might both pass on their genes.
No, we're right to laugh at people who get married in the nude or dressed as Shrek and Fiona and two people of the same gender walking down the aisle is no less ridiculous, just because the state recognises something doesn't mean it's recognisable or acceptable to the people.

Toni Lavis,
Slavery has not been abolished in Western society as you believe, most slaves in Western society are sex slaves. More girls are held as sex slaves then homosexuals seeking marriage. Your sense of justice ought to be vented at this injustice, but no, you overlook real injustice in Western society.

To claim homosexuals are born is spurious, as most same sex acts are committed by persons with failed heterosexual relationships. Like a young man I knew in the 1970's who grew up always keen on girls and developed a close relationship with a girl in his school that lasted for 9 years only to have her leave for another young man, which totally broke his heart at 22, he became a recluse and spent time with his mates and their cars and from there entered a homosexual relationship. He abandoned contact with his parents and other siblings. Homosexuals are supposed to be a natural relationship from birth equal to heterosexual, but they prefer to exclude themselves from family and heterosexual society.

Dear Tony,

<<These days slavery is just not illegal in Western civilisation: it is regarded as anathema to basic decency.>>

Quite so indeed.

Then what about the anathema of the state registering the private intimate relationships of people?

In fact, what about the anathema of some people threatening others saying: "we are the state and you shalt do as we tell you and not as we tell you not, or else we will punish you painfully"? I do hope the day comes sooner rather than later, for surely it will come, that this attitude is also seen by all as anathema to basic decency.

//It is a recognised logical fallacy, Toni Lavis. The Appeal to Tradition: http://en.wikipedia.org/wiki/Appeal_to_tradition//

You learn something new every day.

But the argument was obviously dodgy; blind Freddy could have driven an uncooperative road train through the holes in that line of reasoning.

//There's another one to add to the Slippery Slope and the Appeal to Nature.//

Not to mention the Red Herring, the Non Sequitur, the Tu quoque and other Ad Hominem fallacies, and Question-Begging.

Somebody should be keeping score on this.

//Why shouldn't two heterosexual people of the same gender be allowed to be married and be treated in exactly the same way as other same sex couples?//

Dunno. Jay, do you know what the 'A' in LBGQITA stands for?

//Marriage is about a partnership between a man and a woman wherein she allows him to sire her offspring in exchange for a share of his resources, shelter and his protection, it's a bargain made between males and females in order that they might both pass on their genes.//

I reckon somebody has been watching a bit too much Game of Thrones. I sympathise; it is fantastic entertainment.

Toni, your comparison isn't valid and seems like clutching at straws.
Slavery was never a tradition, never widespread much less a universal building block of society in the UK and rigorously opposed from the date of it's adoption, that's why it lasted barely 200 years.
Slavery only persisted in other areas because of a shortage of manpower and it was an expensive, high risk solution, Spain and Portugal for example didn't have the surplus manpower found in the UK to re deploy to their colonies so they had to shell out for slaves, slavery ended when mass immigration became viable and industrial technology made muscle power obsolete in many areas of endeavour.
Wilberforce won but the economic factors, the fact that slaves cost a bomb and were less intelligent and less productive than free Irish or Englishmen outweighed any moral argument against the practice. When Britain's cities were overflowing and the Irish were starving the argument for slavery became unsustainable, after all a capitalist would have been mad to pay £2000 plus keep for an African when he could get an Irishman for pennies a day.