It is a common misconception that addiction is a choice rather than a disease. What is more accurate to say is that most diseases (including cancer and addiction) have a behavioral component - this is usually how people get exposed to a disease agent. Take a morally neutral illness like the flu for example - people leave their home and go to places where crowds are, greatly increasing their risk of getting the flu.
Heart disease, diabetes, cancer and many many other diseases come from behavioral choices. And just like not ever smoker develops coronary disease or cancer, most drinkers (90%) do not become alcoholic. Something besides choice has to come into play.
Those something elses are environment and genetic susceptibility. So, no, addiction is not a choice.
The accusation that addiction is merely "a choice" has been at the root of a tremendous amount of suffering. Implicit in that claim is the idea that the addict does not deserve compassion. I think this assertion (it's your own fault so you deserve no sympathy) is not only wrong but it's quite bizarre.
Seriously. It's like saying that someone whose behavior causes the death of their own child (say through missing the symptoms of an illness) deserves less compassion than someone who tried and failed. This is upside down.
If you have a hand in your own suffering (and frankly don't we all) then isn't it likely that your suffering will be greater (tinged with regret, self-recrimination and shame)? Wouldn't compassion be most importantly placed here?
Some people hold an unexamined assumption that punishment is useful and that by punishing people who are bad we are somehow helping them. Other people, more than are probably aware of it, are quietly and secretly sadistic and take comfort in seeing others in more pain than they themselves are in.
Alfred P Doolittle schools us on the needs of the undeserving poor.