uhm, that oman verse doesn't apply really, that was more couse oman was disobiedient to gods word.
anyways, mastrubation is bad becouse it's a sin against yourself.
You're not sinning against god, no, against yourself.
But by sinning against yourself you're polluting yourself, by which you're polluting the temple of the holy spirit.
It's that simple.
Imagine you having to stand in front of the prime minister.
How would you go? In filthy smelly rags, unwashed, hair uncoamed?
Or with a nice perfume, clean, bestest clothes, and hair coamed perfectly?
Same with god, if you wish to be in front of god at your best, you stop sinning against yourself, if you don't care? well, go on then, we all have gotten free choise from god.
Michael