The CDC (USA) classifies diabetes as a disease:
CDC - Chronic Disease - Diabetes - At A Glance
Diabetes (type 2) is often brought about by lifestyle.
Labeling something a disease doesn't absolve a person from being responsible for managing said disease.
If you're diabetic and you eat something you shouldn't, you're going to endanger your health. If you're addicted to alcohol and you drink something you shouldn't, you're going to endanger your health.
My urge to drink has yet to go away (will it ever?). My tendency towards addictive behavior has been with me for as long as I can remember. I don't know why I am the way I am. I'm just glad I've been able to shelve one of my behaviors--drinking alcohol.