It’s actually a lot less common for regular citizens to open carry in the US than some might think from US News. It’s unusual in a protest, and almost always a far right thing. It has been used effectively by the left, but not at scale in the last 50 years.

The most effective protest movements usually have two approaches going on at the same time, one that threatens violence, and one that is strictly non violent. Non violent movements tend to be ignored until negotiations with them are seen as more favorable than dealing with an armed movement.