The one thing Dahmer needed that he never received - the thing that caused him to act out bizarre urges - was proper psychological evaluation, counseling, and medication. It's not as if there are not ways to prevent people from killing other people, especially when the behavior is compulsive and irrational - even Dahmer knew what he was doing was irrational. He wanted help, and the way this country treats people with mental illness, he was not allowed to receive it until it was too late.
Ever since a young age Dahmer was showing signs of his antisocial behavior. He grew up with a lack of parental figure which could not be changed once he reached adulthood. He had extreme problems with alcoholism and he was extremely messed up in the head due to his childhood. He progressively got worse and worse to the point where I do not believe he could even come back from. It is believed that he was able to control his impulses during his killings but he chose not to.
Jeffrey Dahmer had no remorse for anything he did. He was so damaged as a young child that his psychopathy was set in stone. Psychiatrists agree that he was past the point where any therapy would have helped him. He was devoid of any sort of empathy or sympathy for his victims. In short, Jeffrey Dahmer had no soul.
To those debating the nature versus nurture question, Jeffrey Dahmer presents the ultimate conundrum. Was Dahmer really a human or only a broken attempt at manufacturing one? Yes, he is accused of killing 17 people which make him a serial killer. But, he was far more. The way he tortured and eviscerated his victims belies any attempt at comparing him to a human being. A creation of Dahmer's ilk was beyond being saved. He had to be destroyed.
Even though for some reason people have the notion that medication and counseling can fix everything. In reality some people are not fixable. He was serious broken and had issues that span far beyond the magic pill and the couch. He was psychotic and enjoyed the things that he did, he did want or seek out help of any kind. Not to mention he did these things in plain sight and no one noticed, this might be a society problem; we have to take off the blinders.
I do not believe Jeffrey Dahmer's psychological problems could have been solved with counseling and medication. I believe that his problems were there at birth and no amount of counseling would have made any difference. His odd behavior started to manifest at a young age and became progressively more bizarre as he grew older. But hindsight is always 20/20. I don't think anyone could have suspected the monster he would one day become.