You need to understand a few things about pornography.  Koz deals with it a lot in his work.  And there are a lot of misunderstandings.

Pornography is an intimacy issue.  People that do not have intimate connections (sexual, spiritual, emotional) can suffer a lot with pornography.  Pornography has a unique effect on people who are lonely because it temporarily makes them feel good.  

It is very possible to develop a serious addiction to pornography.  How do you know if it's an addiction, or a habit or just an activity?  Koz looks at how it's affecting your life.  Is it harming your relationships?  Is it making work difficult or jeopardizing your career?  That's one way you can see if someone is addicted.

It's true, this is a case by case thing.  Different people have different reactions to social media, alcohol, or any other thing that we know can be addictive.