There are many different theories on the origin and continuation of homosexuality in the human species. Most are very interesting, and bring up a lot of questions. In fact, the question, though raised in a confrontational manner, is not a bad one (from the OP).
That being said, most of the people responding to it are lacking, hugely, in knowledge of evolution.
1) The "benefit to society" arguement. Sorry, but that is not evolution. And "read the selfish gene" is good advice, but also for the person who advised to do it. That would be an evolutionary dead end, as the people "helping" would be the ones with the gene, and those "helped" are likely to not have it. Therefor: the gene dissapears. There really is no benefit to having a non-breeding gene. Seriously.
2) Insects. Completely different situation. Those insects with non breeding members are clones. Meaning: they don't breed, but their genes do. So, the behavior makes sense genetically.
As for most of the other answers: They are (most, not all) way too simplistic, meaning you probably don't even understand the problem being posed completely.
Anyway, posters on FSTDT tend to get really self-righteous, even when they have no idea what they're talking about. Maybe we should calm that down.