I think it was about 10 years ago that I first became an LGBT activist in a small way - slash fan fiction started appearing in my Animorphs fandom, and the stories always paired up the boys, leaving the series' two female characters out in the cold. So, being the gender-equity activist I am, I decided to start pairing up the two female characters in order to promote lesbian visibility in the fandom.
Before I started writing slash, I knew homosexuality existed - I've been involved in theatre since I was 6 or 7 and my mom had been doing costumes with a professional summerstock theatre group in Saugatuck, Michigan for a few years at that point (Saugatuck is a popular vacation destination, especially among LGBT people, which is ironic considering how conservative western Michigan is!). But I had also been raised with a lot of ideas about "love the sinner, hate the sin." However I made a startling discovery when I started writing slash: I empathized a lot more with these stories than I ever did about the heterosexual romances I usually wrote and read.
Because books are always where I turn when I have questions, I started picking up every LGBT book I could find: my early favorites were Am I Blue?, Annie on My Mind (of course), and Empress of the World, the book I like to say changed my life and finally got me to start admitting that my sexual orientation was not heterosexual.
So it is as a feminist and a bisexual woman that I choose to highlight LGBT fiction whenever I can, especially YA fiction because that's the genre that helped me so much through my own coming out process.