maybe a little, the vid you posted was indeed a fuckup, and i agree it was unjustified use of force, on the other hand if they're trying to push back protesters to the extent they need to use flashbangs/teargas, the protesters should realize that shit just got real and they really need to gtfo ...
i doubt the guy that got knocked out was hurt by (one of) the first flashbang/teargas grenade ....
so long story short, when you're in a riot/protest it's not all that hard to see/know when you need to scramble, if you fail to realize you're not wanted there when they're throwing teargas/flashbangs (rubber bullets?) then you better accept the consequences ...
Non lethal weapons are designed to take you down, so yea, you are gonna get hurt, you're just not gonna die...