but then, for some guys there are scaled debates on whether masturbating is a sin or not. see, for men it is possible to masturbate without any lustful thoughts lurking your mind, just takes a lot longer with more work.
some say that if you do it without lustful thoughts, you build mental endurance to a lot of other tempations related to lust.
but as for me, i say it is a sin. without all that mental endurance, you know it feels good, and you know you have some dirty thoughts in there. i guess modern society alters things around a bit.
as to conclude, originally masturbating is a sin.