It is far more complicated than what the author is saying. In order to recover from addiction, one needs to decide to do so and have the willpower required to do so, at least when the addiction is being treated in a mainstream, biomedical fashion. However, this letter comes pretty close to saying that addicts want to be addicted, which is far from true. While medical problems may or may not cause addiction, it is very misleading and wrong to say that people are just simply a product of choice, they also usually have to deal with things like social exclusion, lack of opportunities and resources, unfortunate life events, and discrimination. In such circumstances and without a supportive group of friends and family, addiction (as well as mental illness) becomes incredibly common. This is before we even consider potential biological bases/predispositions for addiction, which do have some evidence behind them.
But even if addiction were a product of choice, I think we could be much more compassionate than what the letter is suggesting. While addiction, in my opinion, is no justification for committing crimes and hurting others, there is still grounds to help people who do want to tackle their addiction and also to fund preventative measures that aim towards having more social inclusion.