You definitely are making a moral argument, even if that isn't your intention. There is no meaningful way to define "outside the norm", so it becomes a synonym for "unnatural" and a proxy for individual prejudices. Homosexuality is statistically "outside the norm", and conservative heterosexuals use this logic to support gay conversion therapy and other bigotry. You can overindulge in any dopamine-producing activity, so the same can be said for sex, eating, drinking, smoking, etc. The particular type of sex you enjoy is as irrelevant as the brand of whiskey you prefer.
