I think there is a better way to handle the protests, though DC has easily done the best job of dealing with the protestors of any of the cities so far. Nonetheless, the increasing prevalence of walls troubles me. I think the trick is to understand the different types of protestors.
1. Peaceful legal protestors. These are people who want to make their opinions none, and to interact with the targets of the protest, but not physically impede them or throw things at them.
2. Protestors looking to engage in civil disobedience. These are nonviolent protestors who are willing to violate the law. They seek to prevent the meetings from taking place with any effectiveness by restricting the movement or access of delegates. Alternately they may attempt to gain access to the closed meetings or cross police lines they believe to be overly restrictive. Attempts to gain access and the crossing of police lines is fairly classical civil disobedience as it is the civil violation of 'unjust' laws, though I think we can all agree that the magnitude of the injustice would be far less than 60s civil rights protest. The attempts to restrict movements are differ, but as this is a government meeting they aren't outrageous. Whether these tactics would be legitimate against a non-governmental meeting is a more difficult question and I suspect the answer is no.
3. Protestors who violate the bounds of civil disobedience. These could be rioters, looters, those throwing things at delegates, those who engage in violence, etc. The bounds of legitimate action towards police are wider than those towards other civilians, however, direct violence, and some lesser actions do cross the line.
The police should not interfere with the activities of the first group, out side of basic restrictions such as getting a permit, and reasonable distances between the targets and the protestors. Working out a fair method if its only these protestors is fairly easy, though still open to minor argument.
As for the third group, they are violating the law and not in a manner entitled to respect by a democratic culture. They should be treated as such. Though it should be made perfectly clear where the line is, and that line should allow for actual civil disobedience.
The second group is the trickiest. It is a battle of maneuvers and PR between the police and the disobedient protestors. The police should not escalate to tear gas or severe crowd control tactics unless it is absolutely called for. Mass arrest can be legitimate, but they must have due cause, observers, journalists, and ideally type 1 protestors should not be arrested. However, this is not a game the protestors are entitled to win, the police are entitled to a fair amount of maneuvering room, as these protests do violate the law. Some harassment is to be expected on both sides, and the side that best organizes its numbers will win, this is not always going to be the protestors.
The trick is differentiating between the three types, particularly when they all plan to be there. The police should do more to increase the rights of type 1 protestors. Type 2 protestors have also been treated unfairly, though to a far lesser degree and they'd do there cause well to not whine. Type 3 protestors should be jailed or completely marginalized, for the interests of both sides.
The protestors would do well to make it as easy as possible for the police to differentiate between the types. There is doubtless strategic advantage in type 2s pretending to be type 1s, but that advantage will restrict the freedom of all type 1 protestors so it should be avoided in most cases. The protestors must also work much harder to exclude type 3 protestors, they hurt the movements PR, distract media attention, and give excuse for the most severe restrictions. So long as these hooligans remain a prominent factor, these protests will have there effectiveness crippled.
So protestors, please, get some bloody leadership