Fair enough. The meth thing is kind of funny. I forgot about those types of legal drugs haha.
As for cannabis, I never stated that it is impossible to drive well while experiencing its effects. I just don't think it is wise to assume that just because you are comfortable with it, you are also just as efficient and quick.
Also, not everyone who smokes and drives is good at it, so I rather it be illegal altogether than legal at all. It isn't necessary for >99.9% of cannabis users to be high all of the time, let alone while driving.
When it comes down to driving, I rather a small group of people be inconvinienced vs one person being killed as a result of being "fair". Yes that includes myself.
Not everyone is fit to drive, and if you aren't, efforts should be taken to make sure you don't. If you get away with driving while tired, old, half blind, buzzed, high, tweaked, dumb, etc., you got lucky. It doesn't mean that it's a smart thing to do.
As a cannabis user (yes significantly medical as well, but not "needed" [another point I was making that it can be uncomfortable to be sober sometimes but I wouldn't drive high]) know I rather everyone, or even every cannabis user, on the road with me to be sober vs high.
Sure some would be safe either way, but some wouldn't be safe high, and I don't want that mix to be legal.