well for starters, from your blurb it doesn't make any mention of things not being safer, just that more drivers have it in their system. secondly you speak from a position of ignorance, you put MJ in your head as this big bad thing, but it's a fact, it's WAY safer than alcohol in every regard. you can die if you drink too much alcohol. you will NEVER die from smoking too much weed. you can't overdose on weed. you don't get weed poisoning. weed doesn't make you aggressive, it doesn't make you get into stoner fights. anyone that drinks alcohol but is for banning or limiting weed is a grade A hypocrite. simple as that.
I doubt anyone ever claimed that. Mini bike fumes have probably damaged your brain.
Marijuana users tend to use at home, which could be due to prohibition or simply because they prefer it. So they are less likely to be driving. Also, since it is a substitute for alcohol and causes less impairment legalization will likely to reduce traffic fatalities. The data from states with legal medical marijuana seems to support that.