Dear friends :),
Let's be plain about this: I am sorely tempted to masturbate. I want to do it, and yet my conscience says "no"; now, is my conscience only making me feel guilty by association with Western puritanism, or is this really grave matter?* Why* does the Church define this act of private pleasure as a sin? Logically, I see no sense to it. The only reason I can see the West so vigorously condemning masturbation is out of an Augustinian hatred for the world, the body, and material (dualism). Someone told me that Eastern Christian morality tends to discourage masturbation, but does not condemn it as a sin.
I've read the Catechism paragraph, so please don't cite that. Give me reasons.
Now, how can we compare masturbation to anything else by allegory? I compare it to eating nutrition-less foods, or smoking. We consider a bit of absolutely-unhealthy chocolate now-and-again to be acceptable, or even a pack of cigarettes on a Sunday. These are not considered grave sins, only disordered pleasures! Nutrition, however is the very point of the digestive faculty, and proper-breathing is the very foundation of the lungs. By comparison, masturbation is an abuse of the sexual faculty; so, all faculties in a human body being equal, masturbation can only be a disordered attachment, not a grave sin. The parallel is complete.
If you can eat a big chocolate cake once a year, why can't you masturbate once a year? Smoking? Red wine? Fatty foods? How far can this stretch? We cannot deny everything to our bodies, like gnostics. This is very frustrating because I see no problem whatever, yet my conscience has been formed entirely around avoiding masturbation. :(