How could they keep statistics when there is no test for intoxication?  For alcohol it's .08. There is no analogous level for THC as far as I'm aware. It remains in your bloodstream for weeks.  At best they can do a field sobriety test, but even that is very subjective and difficult to defend in court.  

I'm not opposed to legalized marijuana for lots of reasons, but to whitewash the impaired driving aspect is disingenuous.   I've smoked my fair share and can attest that my driving performance was seriously impaired.   Anyone consuming it has no business behind the wheel while under its influence. 

Comparing it to alcohol or texting is meaningless.  They are serious threats in their own right, but how does that minimize the threats from driving under the influence of cannabis?