Spoiler alert, it's a tiny fraction.
Theft and assault should still be crimes. Usage should not be criminalized. Trafficking should be replaced with regulated commerce.
Long ago and far away I once had a friend who was a speed addict. (Amphetmines) I liked the guy but he wasn't allowed in my house because he would steal shit to sell to buy speed.
So, on the one hand you're not quite wrong. On the other hand, we could have just given him some speed. It's actually pretty cheap.
The real problem is whatever happened in his life to make him an addict. Cops and jail do not help with that.
(There'a a nice ending to this one: eventually he got clean and has been stable for years now.)
And whether the number of thefts and assaults they engage in is all that significant.
Finally, I'm pretty sure moral compass has little to do with whether addicts engage in theft and assault.