Peaceful protests often involve visibly breaking the law. Rosa Parks even did it without cameras! Gandhi, MLK, suffragettes, conscientious objectors, Thoreau etc.

There is a long history of police and intelligence services surveilling and infiltrating peaceful protest movements. Authorities of the day definitely will imprison people.

The big difference is that the QAnon/Trump/etc crazies are planning violent criminal action. Those people end up grouped with IRA/UVF, Nazis, ISIS, Hezbollah, mafiosos etc.