What I object to is the circular reasoning... that it's a sin because it's a sin. Where does the Bible say that 'self-gratification' is sinful? A married individual could want to have sex with a partner to fulfill one's own sexual needs. I mean, even newly weds had no desire to fulfill and ONLY did it for the other party and kept saying, "I want to if you want to" and the other says, "I have no desire whatsoever but I am only willing if you want it" and they were both sincerely, they might never do anything.
Again, lust is desire... or coveting. Where is the line of reasoning that connects with the scripture like-- 'thou shalt not gratify thyself' or some scripture that indicates that masturbation is a sin. There are a couple of pages of forbidden sex acts in Leviticus. Why isn't masturbation mentioned?
Okay, one should not covet one's neighbor's wife, or look up on the virgin with coveteousness. But how does that prove your point?
Let's say a man has no hands and his wife is out of town with the doctor needs a sample, so he uses his neighbor's wife or daughter... through intercourse, and somehow collects a sample. Does the medical exam make it not adultery or fornication.... no. Why would a medical exam make masturbation okay? Or do you think adultery for medical purposes is okay?
Do you think men or boys, or women, did not do this before the advent of photography, porn magazines, or Internet porn?
If it is a sin, why would a medical exam make it okay?
How is this self-evident? Adultery for medical purposes is not okay. If masturbation is a sin, then masturbating for medical purposes would not be okay either, would it? The Bible says thou shalt not commit adultery. Where is the scripture that says thou shalt not masturbate?
Do you think it's sinful if done to alleviate prostate issues for unmarried men? What if it is done as a preventative measure? There are lots of 'medical' reasons.
Man has no hands. Man's wife is out of town. His neighbor's wife has no hands. She offers to collect a sample. He has never thought a lustful thought about her, and isn't attracted to her, but turns off the light, and manages to collect a sample. Does the lack of lust make the adultery okay... since it's medical?
How about this scenario-- the captain of a ship in the 1700s is sent on a mission from the crown to make a treaty with a tribe in a certain country. The chief, as a matter of custom, sends one of his wives to seal the deal, and as an act of hospitality, by having the captain copulate with her. To honor the captain, he chooses the oldest and heaviest wife. The captain has absolutely no lust for this woman, but blows out the candle and does the deed so as not to offend the chief and the accomplish his mission--- sinful or not?
'Everyone knows that' is not a Biblical reason, especially when people are either disagreeing with you or asking you to provide Biblical justification for your point.
Do you drink coffee from time to time? Is that because you lack self control? What about eating pork? If you eat that is it proof of a lack of self-control? Let's establish that something is forbidden first.