As a recovering alcoholic, current caffeine addict, occasional nicotine user, and porn user, here are my thoughts.
I had a complete physical, mental, and spiritual addiction to alcohol. Parts of my life were falling apart around me and I was completely powerless to put down the bottle. Everywhere I went I had to have a plan as to how I would drink, and the possibility of being away from alcohol for a day threw me in fits of panic. When I did quit (years ago), I suffered from acute alcohol withdrawal, including delirium tremens, and had to taper off with benzos to prevent seizures. For me to successfully quit, I had to go to rehab and attend AA meetings everyday for months.
Nowadays I'm a big coffee drinker. If I forget to drink some sort of caffeine on any given day, I will get a headache sometime in the afternoon. I suffer physical withdrawal which is somewhat uncomfortable, but the fact that I could forget to have caffeine in the first place indicates a different sort of addiction than my alcoholism. If I wanted to quit, I would just have to go through a couple unpleasant days and be done with it.
As for nicotine, I've gone weeks, even months without any and haven't suffered withdrawal symptoms, but I enjoy it, so I use it on a semi regular basis, and have been for the last 6 years.
"Addiction" is a term which can describe a wide variety of conditions. As an alcoholic, I have a tendency to downplay addictions that aren't to dangerous substances. However, the author obviously has some mental obsession with pornography, he saw a problem with his porn use, and he felt like he needed some sort of external support to cope with and curtail his use. I don't think the term addiction is wholly inappropriate in his case.
What I don't like as much is applying the label of addiction to other porn users. I think it's up to the individual to be honest with themselves and decide whether they need to take drastic measures to curtail their porn use, whether it's a bad habit, or whether it's just another outlet and presents no threat to their emotional well-being.