Their statement was appropriately hedged. They didn't claim small amounts were harmless, just that it wouldn't hurt in a "serious" way. Your rush to "um actually" someone meant you missed what was being said and "um actually"'d a statement that existed only in your mind. Anyway...
Everyone's threshold for "serious" harm is different.
For adult men, if you drink fewer than 15 drinks per week but greater than zero, the expected decrease of average lifespan is measured in months not years. Obviously more than zero. Is that "serious" enough to not partake? Up to each person.
I have an anecdotal situation dealing with dementia ridden parents from chronic drinking. And similar with grandparents. My risk tolerance is zero for alcohol. besides the lifespan being reduced: quality of life tanks off of a fucking cliff, dragging everyone you love and who loves you down there too.
Sorry to hear that, but your experiences aren't universal. Absolutism is a sensible option especially if there's been problems in the family. It's not the only sensible option for everyone.
Everyone's threshold for "serious" harm is different.
For adult men, if you drink fewer than 15 drinks per week but greater than zero, the expected decrease of average lifespan is measured in months not years. Obviously more than zero. Is that "serious" enough to not partake? Up to each person.