I think it is a good middle ground. You have been able to secure permission from society, who bestows upon you a good size area to protest. The police will be there to protect your safety as protesters from the whims of any counter-protest and are there to protect the interests of society as a whole from any destructive impulses you have for society.
I do not think it acceptable in a civilized society to think of my freedomm of movement to being determined by hordes of men and women acting like nothing better than a herde of buffalo (when they are at their most behaved).
You can be an effective protester, but often a good protester is no different from being a good rabble rouser: you might be good at it, but you are potentially scum.
When it comes to large groups of people moving about in disgust and rage, I do not trust them one ounce. I trust government before I do the good nature of my ellow man in a large motivated group.