Yes I totally see your point the police overstepped their bounds, I can't believe the hell these protestors went through. You see how they're rolling around holding their faces and screaming after the pepper spray hits them. Oh wait they're not, it actually seems like none of them are the slightest bit phased by the pepper spray. So either these are super protestors who eat nails for breakfast, or whatever they're being sprayed with isn't nearly half as bad as you think it is. Plus, after the video when the police manage to finally make a hole you can see at least a dozen officers walking through with a few protestors bound with zip ties.
So basically the protestors were blocking the police from going where they needed to go, the police asked repeatedly for the protestors to move, the police warned the protestors they will be pepper sprayed, the police sprayed the protestors (which again, didn't seem to phase them) and then the police managed to pull one of the protestors out and make an opening to allow the blocked police to make their way through.
Should they have waited longer? Should they have asked nicer? Would you rather have seen the night sticks come out?
Imagine you were carrying a couch out of your house (or any sort of dead weight which would be the detained protestors the police were trying to get through) and you find your entire block is surrounded by OWS protestors holding arms together. You have to get this couch past them eventually and there's no way around to do it. You can't throw the couch cause it'll break (or it'll pretend to be broken, upload a video of you "breaking" it on Youtube and have you suspended), you can't step over the protestors cause the couch is too heavy and you already tried asking them to move but they told you they'll only move if you put the couch back. What do you do?