Here it is in case you missed it, with emphasis:
If you are simply referring to a case where someone was driving while impaired, the same could be said of countless people using cell phones or eating while driving. Do you propose criminalization of food and cell phones? Even while not driving?
So I'll ask explicitly. When you posit a "simple truth: that even moderate use of marijuana can cause tremendous harm", what harm are you referring to? Since much of what's been written here was about the effects of impaired driving I assumed that's the "tremendous harm" you meant. If that is what you meant, then yes, food if eaten while driving can be as harmful as marijuanna.

Or were you talking about some other harm?