It seems to me that nobody can really tell anyone else that they are an addict, because it probably will not be accepted to the depth that it needs to be to make any difference at all for the addict. This has been my own experience and what I have seen meeting many people in and out of recovery.
The conclusion that worked for me was the one I had to reach in my own heart.
Many hundreds of silent nights with masturbation, screaming nights visiting schmutz sites and establishments, phone use for lust, and other disappointments washed over me. I even got caught and didn't stop. I was repeatedly shocked at my failure, after such sincere regret and Teshuvah.
A great Rav told me that the answer was more spirituality, though he had no clue that my very spirituality was twisted and only contributed to my very problem! See, my yiddishkeit had developed during the very same years that my habitual use of lust and schmutz developed into my preferred, safest, and only really reliable coping mechanism and "medication" for the pains and fears of normal life. It seemed to work for many years, though it sucked the reality out of me, slowly replacing true devotion to other people and Hashem with self-absorption. And the yeshiva experience itself - being so self-absorbed in ruchniyus self-development for our future lives... only land-locked me further. There came a time that there were no answers left.
Another Rav told me I needed to explain to my wife that she wasn't enough fun for me. Let's not even get me started on that one, though I bought it hook-lin-and-sinker at the time.... (Nu, osah r'tzon ba'aloh, right?)
Two shrinks told me that I needed to learn how to get more healthy pleasures out of life.... more self-centeredness. Another told me it was no big deal.... and he was frum. Yet another told me that 12 steps was silly, cuz "you want to get better, not learn how to live with this problem." He put me on meds and did therapy for 10 months while I got progressively worse, to his amazement. They all helped me and hurt me a bit, in different respects.
Rabbi Twerski told me (over the phone) in 1992-ish that I'd probably not get better unless I did intensive therapy, went to rehab, or joined a 12-step recovery fellowship. I told him "thanks", and knew that there was no way in gehinnom that I'd be able to hide those things from my wife, and I'd better really try harder! Eventually I couldn't even hide my addiction from my wife and even that didn't stop me (though it worked for a few months - If GYE would've been around then, I'd have made it onto the 90-day chart for sure! ;-) It took me five more years to finally rush myself into whatever help I needed, come what may. I saw that I couldn't stop.
And I came to SA and have been sober since, because Hashem obviously loves me and has the power to help me. But most importantly, I let Him. And I needed a lot of help to learn how to do that, and got it.
So, no. I don't believe anyone can determine for another that they are an addict. In my case the experts were right, but it did no good. As the gemara explains out of the posuk in mishlei, "taychas g'orah b'leiv meivin - meyhakos k'sil meyah". It's gotta come from in my own heart if it'll do any good - a k'sil like me just won't really believe it, until I become a meivin in my own heart.
Besides all that, I find it hard to believe that most of us are smart enough to know if someone is an addict or not. Usually it's trial and error. The only, really sad question we need to ask ourselves is now much evidence do we want? I personally know folks who have been arrested for (blatant) sexual misconduct and still came away from it basically blaming the cops for entrapment, rather than admitting that they have a serious problem.
Along the same vein, I know talmidei chachomim who have been oiver on gilui arayos, schmutz, masturbation, you name it, habitually many times and went for years hiding it (and some still are). And they say they were not hiding it because they want to be able to keep doing it, but because they honestly believe that: "eventually I'll beat this, I know it! Hashem's just got to help me out here! So why rock the boat in the meantime and ruin a great marriage and screw up my children with divorce? I'm trying. I'll do something about it!".
Gevalt. A great marriage? Screw up the children? "I'll beat this"? Who suffers in the mean time while these and many other hundreds of yidden like them are "trying something"? I wonder who has the right to encourage them to stick with the old-fashioned way and learn mussar harder, while the family crashes and burns? What does it do to a 14 year old yeshiva boy to see his father who taught him how to leig t'fillin last year, carted away by police for soliciting a minor for sex in a chatroom (like more than one father I know), or get divorced because of a destroyed marriage after years of secret porn (and what it leads to) driving the parents apart (like other fathers I know)? What wife deserves this?
OK my rant is over, and it's too long to read, anyhow. I love you (even if you fell asleep already!) and am just sharing one little guys experience and opinion.