For PR purposes, they claim to be for "family planning" and women's health, but their main interest is promoting abortion (and making lots of money in the process).
(In response to another poster) I believe that, although they do not gain directly by promoting the gay agenda, it's part of their (very successful) strategy of breaking down traditional moral values.
The socialist organizations of the left have a hundred names but a common goal. This is why "Food Not Bombs" protests the Gore loss in Florida, PETA protests the WTO, etc.
There is virtually no free thought among these people. Sign on to one plank and you must eventually accept them all (the horror that is political correctness).
It leads to such books as: The Sexual Politics Of Meat by ADAMS, Carol J - "The groundbreaking work that introduced the idea that the eating of meat and the oppression of women are intimately connected. Welcome to a feminist ethics of vegetarianism."