See my other comment because i’m not retyping all that shit, but the main issue is the risk of escalation inherent when using chemical weapons regardless of lethality.
The only reason Russia is using CS on Ukrainian positions is because Ukraine doesn’t have Vx stockpiles, and Russia knows no one is going to give them Vx. The same goes for protestors. If cops knew that protestors might start chucking Vx over the line they’d be way more judicious in their use of CS.