I'll leave it to the theists on the board as to whether or not they choose to debate the point of their religious beliefs speak to the morality or immorality of masturbation.
That said, speaking as an agnostic, your point is taken. I have absolutely no qualms about it - and am completely unfettered by any conept of "sin" as such.
Yea I'm coming from a religious standpoint. It's like when Christians tell people that if they don't except Christ they're going to burn in hell. Well that's what a Christian believes, but to a non-Christian, that threat isn't so intimidating. So from a religious standpoint I believe it is immoral (as evidenced by previously cited scriptures). From a non-religious standpoint I believe that like everything else, "too much of anything is a trap."