He’s talking about how the standard unit of alcohol definition bears no resemblance to anything people actually interact with in the real world. For example, one unit of alcohol is ~200mL of a typical beer. When was the last time you saw beer sold in 200mL containers?
He is saying that if you want to communicate such ideas to people you need to speak to them at their level, not something geared towards scientists. If you ask random people on the street how much beer one drink is, they will likely tell you it is one pint (473mL), when in reality that is more than two drinks.
And when one finds out that, they are not going to reel in horror, they are going to laugh at how out of touch someone was to communicate that idea so poorly.
People will still laugh, even if scientists say, that half a beer (250ml) is already bad for you. Scientists need to present facts, if people head their conclusions or not, is not really their problem in most cases. Our society is deeply ingrained with alcohol abuse. How do you think scientists or science journalism should present the fact, that even small amounts of alcohol are detrimental to your health, to the general public?
