Ever been in a detox ward? Ever been in a rehab facility?
You can't use a detox ward and a rehab facility as supporting evidence that alcoholism is a "disease," then turn around and immediately shrug off what Namath himself learned in his rehabilitation program (in what was likely one of the most respected and effective alcohol rehabilitation facilities in the United States, too).
The pathology and progression of alcoholism is well defined. I happen to believe there is a "gay gene" as well.
There may be something that is defined as a "gay gene" or an "alcoholism gene" by medical science, but these will never be definitively linked to homosexuality and alcoholism -- mainly because medical science will have no way of explaining why so many people with these genes don't exhibit any of the symptoms of these conditions.
If you would go to a detox ward and rehab center, you would understand that it is called a "disease". The Namath quote did not exclude that, did it? He simply spoke that which he came to conclude via rehab. It's part and parcel the desired result. A way to deal with the disease.