Tom Chivers is the London Daily Telegraph's assistant comment editor. He writes on science, culture and anything that crosses his mind. Recently he posted a sentiment-driven piece in the Telegraph online in which he recounted how he cried into his champagne at a ceremony he attended built around the civil union of two lesbian friends.
Both his article and the exponentially growing (at the time of writing) file of comments on it reveal the state of bewilderment in which this whole issue is leaving us – we had Kant, Aquinas, Nietzsche, all being drawn into the argument. Semantics are a big contributor to the bewilderment to the extent that you are left wondering if anyone knows what the other is saying anymore – marriage, racism, homophobia, are all up for definition and redefinition.
Poor Tom’s heart was broken because, despite their apparent happiness -- “the couple were painfully obviously in love” -- they were not able to say that they were a “married” couple. Tom’s flood of tears carried us along through the usual allegations of how unfair it all was , how ridiculous were the arguments against it based on the existing institution of marriage as we have known it, and how hatred and prejudice was at the root of it all.
The response displayed, as might be expected, a bloody battleground with the usual sprinkling of ad hominem bile. However, although Tom himself did not mention the Slippery Slope, or the Slippery Slope Fallacy, one commentator gave us the benefit of an illustration of what he saw as the Slippery Slope Fallacy Fallacy.
The Slippery Slope argument is that we are on it and that it began with the introduction of the 1967 Sexual Offences Bill to the British Parliament. The Slippery Slope Fallacy is that this is, well, a fallacy. The process set in train in 1967 is all about removing obstacles to further movement, not causative connections. The Slippery Slope Fallacy Fallacy is revealed in the following timeline and imagined (partly) exchanges over the past 40 or so years:
In 1967, during a lively debate in the United Kingdom over the legalisation of homosexual acts

Conservative guy: "No we shouldn't legalise homosexual activity because it will legitimise it and we'll end up with homosexual marriages, children raised by homosexual couples, 17 year old lads taken advantage of, and laws against criticising homosexuality."

Woolly-minded radical zealot: "SLIPPERY SLOPE FALLACY! Don't be ridiculous. It's just about getting the government out of people's bedrooms, and the age limit will be 21 for buggery and sodomy. And nobody in his or her right mind would ever think that putting children in the hands of homosexual couples would be appropriate. And freedom of speech is sacrosanct."

Lord Arran (sponsoring the Sexual Offences Bill):  "Homosexuals must continue to remember that while there may be nothing bad in being a homosexual, there is certainly nothing good. Lest the opponents of the Bill think that a new freedom, a new privileged class, has been created, let me remind them that no amount of legislation will prevent homosexuals from being the subject of dislike and derision, or at best of pity. We shall always, I fear, resent the odd man out. That is their burden for all time, and they must shoulder it like men—for men they are." 2001: Sexual Offences (Amendment) Act 2000 lowers age of consent to 16.

Conservative guy: "Don't repeal Section 28 because it will free government bodies to spend taxpayers' money propagandising for homosexual activity, and will help to normalise homosexual activity. We'll end up with homosexual marriages and laws against criticising homosexual activity."

Woolly-minded radical zealot: "SLIPPERY SLOPE FALLACY! Don't be absurd. It's just about freedom of speech." 2004: Civil Partnership Act 2005: Homosexual couples adoption of children allowed by Adoption and Children Act coming into force 2007: Sexual Orientation Regulations bar people from acting upon their disapproval of homosexuality 2008: Criminal Justice and Immigration Act creates laws suppressing free speech in respect of "inciting hatred on the ground of sexual orientation" 2012: Tom Chivers proposes full state backing for "gay marriage".
Where next? There were many predictions on that front – but they are mostly unprintable, for the moment. They will probably be common currency in the not-too-distant future.