The sex positive agenda seeks to see everyone active at every age. They want no moral judgments regarding sexual of any kind regardless of sex, age, relation, marital status, number, or species of partner(s).
They are opposed to the notion of abstinence because they see it as a supression of sexual urges. So go f your neighbor’s wife or your cousin. Doesn’t matter.
Everything liberals do, they do to increase their chances of having sex. Everything.