It is “the matter at hand”. It is neither illegal, immoral nor fattening. Technically, it is homosexual; but for the same reason it is sex with someone you love.
To say that masturbation is against God's will is manifestly absurd. If God exists and doesn't like masturbation, then it wouldn't exist. It would be neurologically impossible, like tickling yourself.
(Imagine a world where masturbation doesn’t exist, but self-tickling does, and is forbidden!)
The existence of masturbation proves that, if God exists, then God is not only wise and compassionate, but also has a sense of humor.