Democratic dissent is not disloyalty, it is a positive civic duty
I've been in the middle of a well controlled protest situation in the past. When the G8 Summit was held in Kananaskis in 2002 the protests were in downtown Calgary. Kananaskis was chosen from a security perspective as there is only one dead-end road in and 3,000m peaks to cross to get in the "back-way".
I worked in an office tower with a clear line of sight down to most of the protest routes, what the police did was have a large contingent of riot police and heavy equipment positioned always out of sight of the protestors, typically several blocks away. Police in shirt sleeves and mainly on mountain bikes sometimes with face painting and streamers and other adornments on the bikes to generate a friendly look, pedaled at the front and flanks of the crowd. Basically the police interacted in a friendly manner with the crowd, steered them in a low key manner, but were ready for any issues.
Over the days of the protests there wasn't a single window broken or anything that resembled a riot, unlike the previous G8 Summit in Genoa that was quite violent. Plenty of low-key police presence combined with meticulous planning and lots of crowd control psychology was the key.