There is likely a combination of social and genetic factors; while the social factors mentioned in the article affect the rates of alcoholism, there is a significant genetic component, which the article claims has no evidence, but ignores the evidence that exists!
Alcohol metabolism in humans varies among populations, with some having a greater capability to metabolize it. The article fails to even mention the purported genetic causes (lack of ADH or ALDH), which would seem to be important if you are going to claim that the existing evidence is wrong.
That genetics affects rates of alcoholism is not a controversial opinion: the NIH has a report on the variance caused by genetics ( http://pubs.niaaa.nih.gov/publications/arh301/3-4.htm ), noting that "Native Americans and Alaskan Natives are five times more likely than other ethnicities in the United States to die of alcohol-related causes. Native Americans are predisposed to alcoholism because of differences in the way they metabolize alcohol."
This makes sense when you consider the environment of the social sciences today, which favors nurture over nature. Anything that is influenced by social interaction (e.g. stress causing alcoholism) must be caused by it, even if there actually are genetic influences.
Unfortunately, there is a cost to the emphasis on social interaction. Suppose that some people have a genetic predisposition to alcoholism, but they believe that it is caused only by social factors. Then they will be more inclined to put themselves at risk by drinking with friends.
(A similar argument for genetic testing can be made for the APOE gene, which modulates risk of Alzheimer's from drinking. For instance, people with APOE 2/2 are LESS likely to get Alzheimer's if they drink, while those with APOE 4/4 are MORE likely to get Alzheimer's. Claiming that Alzheimer's is caused merely by social interaction while ignoring this genetic effect leads to everyone being worse off).