The way I see it (coming from a predisposed addict), is by asking the biological question: how does this genetic disposition benefit someone? If there are benefits, how can it be a disease? After all, which ever way an "addict" chooses to channel their behavior is only a symptom or side effect.
Tenacity! Human beings need to be tenacious to "get things done." I excel, with compulsivity, at anything I personally enjoy (whether those values are natural or nurtured). The same is with a junkie: they may not have a job, and could care less about their family or themselves, but when it comes to their addiction, they WILL find a way to get, they WILL have all the proper tools to execute the activity, and they WILL be an expert on what ever it is they are putting in their body.
I see this trate being merely a human behavioral necessity that just happens to be more concentrated in some than others.