system
A chat on subreddit /r/NoStupidQuestions
human
I completely agree with the above.

As someone that lives in Portland Oregon and sees the nuances between anarchists, protestors, etc, it's important to realise that there are a lot of bad actors at protests who are there simply to escalate the situation. Some are  anarchists that show up to protests that want to riot and cause chaos. There are righties dressed as antifa who come from the back of crowds and throw stuff at police so that the police tear gas and go after and punish the protestors. This isn't a guess, but something city officials have documented and spoke about. 

All of these different groups clash and interact in a very naunced, complex, and difficult to understand way. A simple label of antifa is easy to understand. A single enemy is easier to objectify and hate. 

The right vs left narrative makes it harder for people to switch sides. Citizens are too busy fighting and pointing fingers amongst themselves to see they are being played. It's convenient and cheaper to market to a group of people if their neeeds and wants don't change. and so on and so forth
gpt
In 2001 during the 3rd Summit of the Americas in Quebec City, there were people who were hired to instigate conflict with the police, allowing them to justify their use of force. This was well documented at the time. I believe that there was also a documentary made about it.