Keep Marriage Special: And Incest Too

"If the only basis for marriage is the desire of the parties to get married then there is, according to the logic of this proposal, no reason not to open up marriage to more than just same-sex couples. Polygamy, polyandry and incest would all be permissible."

From a pamphlet published by new looney tunes group, Keep Marriage Special;
"Our aim is to defend the biblical definition of marriage and to oppose any possible redefinition by HM Government."
Good for you. 
Quoted in The Observer - who've illustrated the news item with a rare photo, above, of a gay couple with their heads and faces showing!
Of course, it would be churlish to point out that both incest and polygamy are sanctioned by the Bible.