I understand your point that it is impossible to shelter people from information on the internet, but remember that there are people of all ages reading the stories on this site, who may or may not be ready to read about every topic (and I'm not referring specifically to homosexuality here). I also want to point out that summaries are usually not a good way to judge the total content of a fic. Most authors use summaries as a sort of 'teaser' to give readers a hint at the story, but not the full synopsis.
If people are uncomfortable with same-sex pairings, it's not like by getting rid of the category they are going to be forced to read these stories. They have the ability FOR THEMSELVES to consciously decide not to read a story because it isn't to their tastes. Summaries are there for a reason, after all. If someone doesn't want to read slash, he has the ability to avoid those stories if he wishes, whether the category exists or not. People don't really need to be protected from things that might offend them on the internet (which is hugely diverse, so going about shielding EVERYONE from what offends them is ridiculous, anyway). There is a ton of material on the internet that I don't want to see, or that makes me uncomfortable, but it's easy to simply click out of the window. (Also, the idea of homosexualtiy being offensive doesn't sit well with me, though I suppose I can understand it making people simply uncomfortable.)