Question about masturbation.?

Many people says daily masturbation is harmful. It may spoil our marriage life. What i am asking is that if a person marry in a very earlier age like 20 or 21 that man surely will have sex with his wife. He may have daily or thrice a week. Is it harmful? Instead of inserting the male organ into the female, he simply doing in his. Whats wrong with this? I dont think that masturbation is harm. The man who masturbate is under harm. The man who sex with his wife is not harm. What is this. . Very funny.