OWS' public image was already good, amongst many liberal types who were likely on their side to begin with. With this, they broaden their base and gain support, thus improving their image in the eyes of the people that they want to reach: those that aren't in the choir.
This is an, admittedly very good, effort to get those who are on the fence off it, and over to their side. Yeah, it'll cost a lot of money, but it'll be well-spent when their ideals gain broader support.
Also, I think what Rookie's trying to say is that a lot of people see liberal protestors as lazy college kids who just want to mooch off the government and smoke dope whilst playing acoustic instruments in a public park like a buncha tools.