Folks who abuse cocaine regularly cannot be successful long term. The same is not true for pot.
There is no comparison, and your argument is not a strong one.
Sounds like a variation on the "no true Scotsman" fallacy. My own personal experience with weed smokers is that they often gravitate to other highs, and they no longer bother with weed when they can find something better.
I used to know a pimp that hooked young girls by starting them off on weed, and within a week he had them smoking crack. Weed was just the icebreaker.