https://www.washingtonpost.com/news/morning-mix/wp/2014/08/1...
(Of course we can discuss if most of the uses of tear gas are wrong, but lets for a moment think that we have a moment were we need to chase away a crowd of evil persons riotong and threatening to kill perfectly innocent children.)
At that point, I think the full spectrum of force (including lethal force) is fair game.
Now if we take a situation like the present one, where there is a mixture of peaceful protests, and riots that threaten property, I think the response is different.
Firstly, immediate escalation from the police only begets escalation from protesters. Start with officers in uniform and somebody with a bullhorn. You shouldn't need riot gear unless the rioters are violent towards police. If the rioters start throwing things, upgrade to police in riot gear with shields and batons.
Responding with tear gas and rubber bullets should be saved for if the police are utterly unable to contain the riots to within a certain area. Building barricades and waiting them out is a potentially effective option. Yes, there will be property damage, but that's pretty much a foregone conclusion. Build the barricades, arrest people as they leave the area.
There are also other less than lethal options. Pepper spray seems like an effective system with minimal harmful side effects. There is an acoustic system that generates painfully loud sound (although I believe it comes with a risk of permanent hearing damage). Batons and riot shields seem like an effective system. Regular old vision obscuring smoke grenades would cut out some of the mob mentality since you can't see everyone else rioting.