Key phrase "when protests turn violent." But not before then. If you want to see something heartbreaking, the New York Times has a video presentation of how two SWAT teams trapped and then tear gassed a bunch of non-violent protesters in Philadelphia. It's appalling. But, yes, if a protest turns violent - or is co-opted by people intent on being violent - those need to be stopped. The purpose of a protest is to be heard; it should never be to harm others.