Continuum fallacy?

I see the potential Argument of the Beard , but think McNamara Fallacy may be more germane.

The assertion about more than 1 glass of milk/day is a rate statement and is perforce an average.  If the research did not make it (its "average" basis) clear, the research included some sort of fallacious concept.  If the research did make it clear, the concern about the exact limit (one and only one/day) is taking the conclusion out of context.

The argument of the beard would become a Zeno paradox if rate were included: at 1 plucked hair/day, when does the bearded man become unbearded.  That is not part of the beard fallacy.

Thinking about this a bit more, I think your brother was committing an Argument of the Beard . Here is my reasoning: If someone says that adding a drop of water to glass each second won't overflow the glass, then asks you "will one more drop overflow the glass?" The answer would be no, not "yes incrementally." So if you wanted to argue fallacy, this is how you can do it. Really, it could go either way.

Hello Dr. Bogdan and welcome to our community!

Him: But drinking one more glass of milk today (exception) will not harm you in any way, right?

I am not up-to-date with the current research and recommendations for milk consumption, but let's work under the assumption that 1 glass of milk per day is the maximum healthy amount to drink. Let's focus on the fallacies and not the science, as well. If this is the case, the drinking more than the maximum recommended amount will harm you, but only incrementally, even if that harm is in the increased probability of something more serious. Think of it like death from 1000 paper cuts.

Given your answer, I wouldn't call him out a fallacy, although I would bet that even if you answered as I wrote above, he would still go down the same path which is, as you point out, an Argument of the Beard .