The point being made is that alcohol is legal, and massively harmful, and the public health measures around alcohol aren't great, and so maybe we need to be cautious when decriminalising and legalising other drugs to ensure that we have some health protections in place.
At the moment we don't have those.
We have strong denial in lots of people that cannabis might cause harm in some people.
All the stuff currently being said about LSD, MDMA, ketamine, etc was also said when prozac was introduced. We need to watch out for pharma companies who'll take something that's probably effective in some people (ketamine infusion for people with severe and treatment resistant depression) and rejig it to make it patentable (eskatamine) and repackage it so it can be used much more widely (nasal spray instead of infusion) and marketed much more widely.