The sex tag seems almost pointless. Soooo many pics would have it that you might as well just look at images by more specific forms like vaginal and oral and anal.
But if want to search for pictures tagged as vaginal, oral, anal, etc. in general, and not a specific one, what would you do without a "sex" tag? Multiple search?
I don't think a 6 tags search (thing that not everybody can do) is enough to cover all the variations to the "sex" tag.