I believe his point was that the research is more conclusive that alcohol leads to psychosis than hallucinogens.

And people (in general) aren't all that great at controlling alcohol dosages. If it wasn't for the bodies natural reaction (becoming incapacitated), people would die all the time. How many times have you seen people vomiting (in the bathroom, if we're lucky) or passed out due to drinking too much?

If you mean dosage per drink, I'd again they say that falls out naturally based on the amount of alcohol people can handle to taste, rather than proof of rational control.