Occupy did not only protest. It ran itself. Decisions were made in a General Assembly: an open meeting in the park where anyone could speak and the group tried to agree before acting. Holmes writes that the assembly called itself "an open, participatory, and horizontally organized process." Horizontal means no boss at the top.
The police did not allow microphones. So the crowd used the people's mic: the speaker said a few words, and everyone nearby repeated them loudly so people at the back could hear. You can hear it in the Žižek clip.
Why no demands?
A demand asks the people in power to change something. That means it accepts that they have the power to decide.
One way to read Occupy: by refusing to send demands, the camp refused the system's rules for change. Its answer to the question "What do you want?" was the camp itself: the assembly, the people's mic, the shared food. The message was shown, not declared.