Refined sugar is still nutritious. The human body even has an enzyme (called sucrase) specifically for breaking down sucrose into glucose and fructose. The glucose can go right into the bloodstream or be stored in the liver as glycogen. The fructose portion is processed by the liver, where it is eventually stored as fat.

Given the near-universal appeal of the taste of fructose, as well as historical relevance of fruit to the human diet, makes it seem reasonable to believe that humans are well-evolved to tolerate reasonable levels of fructose without suffering any ill-effects. Even moderate amounts of stored body fat are fine.

Alcohol, meanwhile, is not a nutrient. Most humans have a strong aversion to its taste and must train themselves to consume it and even then the flavor is often heavily disguised. Although the body can derive some energy from ethanol, this is only by way of a complex metabolic process that can cause serious acute and chronic liver problems[1][2]; not to mention the risks of alcohol poisoning. The pleasurable, euphoric effects of blood alcohol serve no physiological benefit and directly interfere with cognitive and motor functions. While there may be some potential ancillary benefits of moderate drinking on cardiovascular health [3], the mechanisms and parameters of this are still not well-known or well understood.

[1] "Acute Alcohol-Induced Liver Injury" http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372892/

[2] "Alcohol-Related Liver Disease" http://www.liverfoundation.org/abouttheliver/info/alcohol/

[3] "Alcohol and Heart Disease" http://www.hsph.harvard.edu/nutritionsource/alcohol-and-hear...