I would say it is a non sequitur rather than an ad hominem.

The article is about the rigor of a paper on the harms of relatively small amounts of alcohol consumption. The comment is about the obvious harms from large amounts of alcohol consumption. The two things are barely related beyond, perhaps, the title of the article.

We can at the same time recognize the harms of alcohol, while also caring about whether there is a relatively safe dose with which to consume it.

As a parallel, we can look at substances as banal as finasteride or aspartame as examples of where we are actually quite concerned about the safety of the small dose, while recognizing the obvious dangers of consistent, large doses. In all three cases (ethanol, finasteride, and aspartame), the "benefits" of each drug are unrelated to health, but meaningful to most people. The main difference is that ethanol is much easier to consume at dangerous levels, likely because regulation is quite difficult, especially when you can make it at home relatively easily.