Is masturbation part of God's rigorous design on sex?
Lon, have you ever "pleasured thyself"?
Er, remember there is a kid-friendly encouraged expression here on TOL. Scripture says some things are too crass to be mentioned/discussed so a puritan mentality resides that you probably aren't aware of and/or don't understand. "Your" mind went here, mine did not. Part of this means that I try to discuss fleshly matters after a fashion that makes sense and is appropriate even and especially to children. There then is an obvious difference between our paradigms, one on fleshly cravings and desires, no? I've been on sabbatical lately because I've been endeavoring to give a reason for the hope that is within me.
We could have better conversed over 1 Corinthians 6:13-15 and talked about 'if I have ever sinned' but all discussion about physical cravings is missing the goal and seeking excuse. If your god is your stomach (physical passions) and you neglect/deny you are spiritual being, you are missing the point and may never be able to actually get the point.
Let's clean up the conversation: If you live to eat, instead of eat to live, you and I are two completely different beings on the planet. Your advocacy is strictly and adherently tied to physical fleshly concerns and thus are concerned primarily with self, egocentrism, selfishness. This doesn't mean you can't do some unselfish act. It means your 'reason' for doing so is not at all the same reason I do that same thing.
Concerning your question, the apostle Paul said "All things are lawful for me/us, but not all things are profitable."
So, the question isn't whether you or I over-eat but 'why' we'd do so. I am repentant for all my harms against God and humanity. You are not and accept harm as normal and okay, especially if it seems only against "God." That is where the difference lies. Whether I sin or not isn't the proper question. How I feel about it and how that is different than you, is. Either I am god, or there is another. Either you are god, or there is another. I came to the conclusion long ago that He must be God and I cannot god myself. You must necessarily, one way or the other, come to that same conclusion. It is inescapable as necessity.
Primarily, this is why there is also an inordinate and disproportionate commercialization of homosexuality is prevalent as well: It echos every other person's self-interested hobbyhorse and egocentrism and celebrates that willfulness 'regardless' of effect (such as is the definition of "god is the stomach" and self-interest.
Is your interest in justifying physical self-interested acts, or does it have a noble spiritual purpose? How far beyond yourself does your interest in this subject go? What is the purpose of your own question? (rhetorical/reflective)
It is a little like saying if anyone ever got a speeding ticket, speeding laws should be repealed (again, self-interested without concern for God or others).