I like the comparison you drew, and your points are well taken. I would add that there's been a lot of research on coffee, and the consensus is that for most people, it has net positive health effects. There's a lot less research on cannabis, which means we're still trying to figure out the true effects, and what we know now is that aside from medicinal uses, it's got some notable negative side effects that deserve mention (as we learn more) and consideration by anyone considering its use.