Disease, illness, character defect, spiritual malady, etc..... No matter what label is put on it alcoholism is a serious problem that kills people and destroys lives.
Personally, I choose not to worry about the label, just the results. That is what I treat. I don't have to fully understand cancer to seek treatment for it. I don't have to fully understand or label diabetes or put a label on it to seek treatment for it. I don't have to fully understand depression, bipolar, or PTSD to know that I need to seek treatment for it. There are people who will debate whether or not mental illness is a disease or not, just as people will debate alcoholism. Either way, both are serious and should be treated.
I must say, I have read some interesting thoughts on the subject within this thread.