Well, the internet can be a good way to discuss personal issues with people that you don't regularly get to in real life for one. This is especially the case for those who are insecure or not "out" about their sexuality.
Also, there are numerous news and discussion threads on LGBT issues since homosexuality is becoming a high-profile issue with polarizing views. The number of threads simply mirror the number of propositions, amendments, controversial television/movies/news stories, and personal experiences (the good and bad) that are pertinent to the LGBT people.
Issues like racism, although sometimes discussed on PC, are issues that have a lack of polarity. The vast majority of people regard racism as unacceptable and the limitation of rights to racial minorities to be an atrocity. Since almost all people are on one side of the issue it is not something that we see as much, but we will encounter a few controversial stories that pertain, including the Tray Von Martin case from time to time.
So, I don't think that there are too many LGBT related threads, and if I did, I would just not read them. I am not interested in reading about life science threads, but I don't think I should voice that there are too many of those threads, and hence they should not be created.