Law enforcement has more important things to do than babysit protesters. Protesting always draws law enforcement from where they are needed and many times causes OverTime pay due to the necessity of extra staffing, at cost to the taxpayer.
I would say that peaceful, lawful protest should be unchanged. Laying about in the street, defacing property and failure to disperse should come with a fine. If you feel strongly enough to do these things, you should feel strongly enough to accept the consequences. A 'fake' arrest costs money. They should pay it.
Free speech and freedom of expression are the foundations of this country. Just add personal responsibility. Protest to your heart's content...just put your money where your mouth is.
I don't focus this on anti-war protests. This should be the rule for all who gum up public areas. IMO.