Earlier quoted context omitted.
Technically, there are ways to prevent some of the harms of marijuana: Using e-cigarettes and using marijuana strains who mostly contain CBD(which generally has positive effects) and little THC(which creates feelings of paranoia and might have mental health risks) , so there are possible regulatory means to reduce lots of the risks without reducing tax revenue.
How can you know which strains contain more cannabidiol?
I don't know how well-tested these strains are (aside from, "puff... yeah, man, that's awesome"), but there has always been a desire in the medical marijuana market for selection based on this data which I'm sure carries over, so I suspect that now that it is legal in a couple of places, we'll begin to see Consumer Reports style testing. Hell, maybe even the Consumers Union, themselves, will get on the case.