In American most of the time we don't have protests we have full scale riots. I have only seen a few cases where a peaceful protest has occured but that is a minority. A majority of the time there are riots. For example the BLM riots and the election riots. Those cry baby liberals have made it inhumane to use any other method of crown control. The water cannons would be a good start.
It should be the right of free citizens in this country to peacefully assemble and protest. However, in a situation where tensions escalate and physical violence ensues, police should be allowed to use water cannons on the protesters in self defense - or in order to protect the well-being of another group of citizens who are in danger or under attack.
Using water cannons on protesters is a more safe way to clear the streets than other methods. Tear gas is more harmful to people. Certainly arresting people isn't as good. Water cannons are probably the least expensive of the options as well. There is nothing wrong with the police wanting to open up the streets for legal commerce.
Protesting to have your voice heard, should not give the police permission to become unlawful. We can all have a differing opinion without it resulting in violence against one another. In my opinion, it is an unlawful act, regardless of their police training or the higher command ordering such action. This type of action was displayed back in the 1960's, and it was wrong then, just as it is now. It will not serve the public's trust or make the situation any better by continuing with water cannons on the protestors. If anything, it could become worse before it gets any better. When the voice of the protestors can be heard and validated, then the water cannons will not be a thought to begin with. It is now becoming the very problem that could escalate the situation, from what really was only a right to be heard, respected and understood.
As the Dakota pipeline protests continue, the police are responding in increasingly aggressive ways. One example of this is the use of water cannons to dispel protest activity. Unfortunately, these cannons were used in the middle of a freezing cold night. This is dangerous to individuals' health and well-being, which goes far beyond protests.