A friend told me that I really need to read First Things Magazine this month man was he right. It tells you why the church will never accept contraception and why the Episcopal communion's movement towards gay marriage and gay clergy started when it accepted contraception. You can find the whole text here.
The adversaries of Humanae Vitae (The Pope's 1965 encyclical that clarified the question of contaception) also could not have foreseen one important historical development that in retrospect would appear to undermine their demands that the Catholic Church change with the times: the widespread Protestant collapse, particularly the continuing implosion of the Episcopal Church and the other branches of Anglicanism. It is about as clear as any historical chain can get that this implosion is a direct consequence of the famous Lambeth Conference in 1930, at which the Anglicans abandoned the longstanding Christian position on contraception. If a church cannot tell its flock “what to do with my body,” as the saying goes, with regard to contraception, then other uses of that body will quickly prove to be similarly off-limits to ecclesiastical authority.
It makes perfect if unfortunate sense, then, that the Anglicans are today imploding over the issue of homosexuality. To quote (traditionalist) Anscombe (Society at Princeton University)
If contraceptive intercourse is permissible, then what objection could there be after all to mutual masturbation, or copulation in vase indebito, sodomy, buggery (I should perhaps remark that I am using a legal term here—not indulging in bad language), when normal copulation is impossible or inadvisable (or in any case, according to taste)? It can’t be the mere pattern of bodily behavior in which the stimulation is procured that makes all the difference! But if such things are all right, it becomes perfectly impossible to see anything wrong with homosexual intercourse, for example. I am not saying: if you think contraception all right you will do these other things; not at all. The habit of respectability persists and old prejudices die hard. But I am saying: you will have no solid reason against these things. You will have no answer to someone who proclaims as many do that they are good too. You cannot point to the known fact that Christianity drew people out of the pagan world, always saying no to these things. Because, if you are defending contraception, you will have rejected Christian tradition.
By giving benediction in 1930 to its married heterosexual members purposely seeking sterile sex, the Anglican Church lost, bit by bit, any authority to tell her other members—married or unmarried, homosexual or heterosexual—not to do the same. To put the point another way, once heterosexuals start claiming the right to act as homosexuals, it would not be long before homosexuals start claiming the rights of heterosexuals.