Which is why I've asked the question. As I stated in the OP, I am interested in showing that consent isn't the best determiner of legitimacy of sexual behavior.
I'll try again. It's not singularly determinative, but it's important. The lack of consent, through coercion, fraud or force tends to be at the root of impermissible contract and conduct. So as baselines go, starting points, it's a pretty good one.
But criminal activity can meet that, so there's obviously more involved. Typically an examination of the conduct in terms of its impact on other right and the state itself. That is to say there are competing interests.
Is it true that people use the terminology of consent to justify some behavior?
Justify? How do you mean? That's more typically the word used by someone who disapproves to people who don't. So one man's explanation becomes his opponents "excuse" if you would. I suspect that when someone says, "They're consenting adults" what they're saying isn't an attempt to justify, but an argument in brief that what's happening in the instance, objectionable as it might be to you or me or the Hindu guy down the street, is that our subjective objection fails in the face of that absent more, that it's really and ultimately their business and not ours.
It seems obvious that they do. Nowhere have I attempted to claim people believe that consent excuses all sexual behavior, only that consent is used to legitimatize many behaviors that have been stigmatized in the past.
But that needn't be the case. I'd note consent and the following argument for people engaging in fornication. "Legitimization" doesn't enter in, because that's another "excuse" word. A thing is legal or it isn't. You can use your right to accomplish it or you can't. The morality of it is a separate matter and the valuation on that point will vary from perspective to perspective.
:e4e: