Well, you can die with heavy dose of water too. Actually not even that heavy, people have died drinking like 7-10 liters.
>The side effects of moderate use of pretty much every controlled substance are pretty much insignificant
Yeah, but the research shows moderate use of alcohol not only doesn't have bad effects (even if insignificant) but it even has significant (measurable) beneficial effects.
Citation? Also, what's 'moderate' use for you? A 'standard drink' equals about 10 grams alcohol, the German institute for addiction (DHS) says* that the threshold dose for risk free consumption is at 20 grams per day, with two days break per week. Above you are risking a plethora of health risks, from mouth cancer, to liver deseases, breast cancer and what have you. There are some benficial health effects, but none of them are 'significant'.
*http://www.dhs.de/fileadmin/user_upload/pdf/dhs_stellungnahm...
There are many ways to judge the statement 'most harmful drug', so there's no bright line, but that's a pretty big mark against alcohol.
[0] https://en.wikipedia.org/wiki/Delerium_tremens [1] Ibid.
Oh, and they controlled for the obvious correlations too, like lifestyle differences etc.