This seems to lead to some interesting ramifications.
It seems, then, that the only reason masturbation is wrong, in your opinion, is that it does more harm than good.
This means:
A) that you believe that any activity where the harm outweighs the good is wrong to do
B) that it would be just as wrong for a spouse to masturbate their partner, since it's the physical effects of masturbation not the auto context that is the issue
Is that right?
If so, can you be clear as to exactly what harms and what benefits come from masturbation, so we can see the pros/cons and why you think it more harmful than beneficial?