No, addiction is not a disease. This is not a widely held position, but seems clearly true.
Consider a disease such as cholera, which cannot be fixed by a choice of the person who has it. Contrast this with being addicted to cigarettes, which people fix by quitting every day. There seems be a significant and substantial difference between the two so much that the same word should not apply to both of them. I highly recommend the following website as a resource for this subject:
http://www.schaler.net/
So in answer to your orignal question, if they aren't using it metaphorically, they should be.