An online protest is equivalent to one in the real world. It is an organized expression of opinion.
There is as much attention online as there is offline. Attention depends on media coverage. A small local protest of 50 people never gets much coverage. But 10.000 protesters are noticed. You bet that 10.000 online protesters get media coverage.
Protest posters are available as virtual items. Organizers can drop posters from their backpack to the Web page.
A speaker can talk to all participants. A speaker item manages the live stream.