Myth 3 is most interesting. The problem with the claim is that it implies that masturbation is somehow "junk food" in a way that sex isn't. Most people I know would suggest the opposite: sex is preferable to masturbation, which is a poor substitute.

Furthermore, the evidence that it is bad consists of two anecdotes, one from a true addict (which is a problem), and one from a man who stopped for less than two weeks. As far as quitting goes, the trouble is that there is no reason aside from willpower in most cases. You save (at most) half an hour or so, during which you probably wouldn't have done anything anyway. What you get in return is orneriness and frustration.

Remember: people have sex drives. They aren't bad. Fulfilling them isn't bad either. Just keep it in moderation if it starts to interfere with life.

Also: without porn, where would the internet be?