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.)
But, we have de-escalation tactics, riot shields, smoke canisters, and literally guns.
If an officer wouldn't fire a gun, I think he shouldn't use tear gas.