Yeah, protests can suck all around.

Then why protest?

Well, the problem is that the message is directed to the "recipients" through lots of human buffers: police, administration, city and county services who have to maintain the peace. I don't have any alternatives to recommend, but the point is to gain media attention and it seems that could be done without messing up the work days of many people who are frankly unable to make any of the changes requested. And it creates an "us-them" polarizing attitude between the buffers and the protesters, where the message was initially intended for someone else!

The second point might be to empower individuals by proving the strength of organizing masses. As long as they are peaceful and unified, participants could benefit, by the context at the very least.

I don't know. Maybe we are on the verge discovering of other types of ways to make change. 

At the very least, and in no way am I minimizing the impact of participation, the clever signs are always awesome!