alt Hacker Newsi don't agree, i think you are just describing a measurement problem, we have a clear mechanistic understanding of why 'anything above zero' would be bad, and are able to measure this in sufficiently large populations for larger drinkers. the effect size is smaller and thus unmeasurable above the noise floor for one glass a night, but the mechanistic story is clear.
Simple mechanistic explanations in biology are often wrong. For example, oxidative stress does not have a linear no-threshold harm.
For alcohol, almost every big study has shown either no discernible effects going from zero to 1 drink per day, or actual slight benefits going from 0 to 1 that then reverse when increasing beyond that. There is not strong consensus which of these is true, but there's definitely no real evidence that 1 drink per day is harmful as measured by all-cause mortality.
See GBD 2020 in the Lancet (which showed a slight J-curve), Wood in the Lancet 2018 (optimally low risk at 100g ethanol per week, or ~1 drink per day), Zhao in Jama (no discernible negative effects at 1 drink per day, no benefits either, no J-curve), and the latest National Acadamies review showing lowest all-cause mortality at about 1 drink per day (so, a J-curve).
Alcoholism has tons of negative effects. But these seem to start at around 2 drinks per day and rise rapidly from there.