I suppose you're right tarmac... It would be very interesting to see, however, what would happen if somebody started an organization that promoted heterosexual sex between 13 and 14 year old girls and middle aged men. Equally sick, but not quite as twisted in the classic sense of the word.
Since gays have become a sympathetic minority in the last 2-3 decades, their causes carry with them an air of untouchablity, especially among the liberal public. So, now, after the initial hysteria of the polically correct 90s, people are starting to push the envelope created during the 70s and 80s. Being gay is less and less taboo, great, now lets see if we can squeeze some legal pedophilic sodomy laws into the pocket while we're at it.... Not the same for mainstream causes. Try to promote the love between a young girl and her dad's buddy Phil and you'd get crucified.