And why would one ever think a moral code or social convention was not the kind of thing flexible enough to articulate what is proper, what is not, when the rule can be broken and when not, and what to do about breaking the rule and what not?
I've stated the reason before: Sexual relationships are so complex that human language cannot properly describe them, let alone be used to formulate moral prescriptions that would apply in any reasonable manner.
I'm getting bored of you mumbling "naturalistic fallacy" without your actually comprehending what you are talking about. I've replied to that multiple times and you haven't once demonstrated that you have the intellectual capacity to comprehend what is being said to you. As such it's hilarious that you think you can "refute" something you haven't even demonstrated that you understand.
The claim is that it's wrong to prescribe against something that is normal, healthy human behavior. That is an ASSUMPTION. It's not a point that I'm trying to prove. You can disagree with that assumption, which puts you into the "we love death more than you love life" camp of theologians, in the good company of Osama bin Laden, and his ilk. Certainly it's a logically consistent position.
I've made it clear that is an assumption. You CAN disagree with it. As I said--I choose life.
Once you've accepted that assumption then we just need to look for evidence that a behavior is natural, healthy human behavior and at that point we can apply the assumption--no naturalistic fallacy.
It would be nice to see from you some evidence that you've rubbed your two neurons together and managed to comprehend the point, first, before you make another pathetic, failed attempt to refute something you don't even understand.