Maybe, they fear that GLBT-related sites lead to inappropriate sites such as porn or nudity?
I remember when a friend of mine at school was doing a research paper on watersports such as waterskiing, wakeboarding, tubing, etc.
So, he did the most simple thing anyone could do...
www.water sports.com
What happened? It took him to a porn site where everyone piss on each other. It scared the hell out of him and got some weird stares from other people who were sitting next to him in the library. Eek!