Ever been tear gassed? I have.
Tear gas is also quite painful, and can cause permanent problems in some cases. It has the disadvantage of not being very precise in a breeze, which is how I got nailed, nowhere near the protest.
Besides, you don't think cops in riot gear with hoses and tear gas are at least as "fearful and intimidating" as one of these projectors would be? The cops have guns, too.
