Peaceful protests says "peaceful" for a reason: because they're peaceful. During one of these protests, there is absolutely no need for conflict or any type of violence. Those participating in peaceful protest do not mean to enact violence or conflict, but to start a movement to change something that they care about.
The right to assemble and protest peacefully should be supported by all citizens. It is the only way to call attention to an important issue without violence. Adequate police protection and courtesy should be extended to the protesters and no arrests should be made if the crowd is not causing harm.
Peaceful protests should not be targets for violence. Unfortunately, the words "peaceful protest" are an anomaly anymore. It seems like every protest that starts out being peaceful ends up turning into a riot with looting and destruction. When protests cross these lines, force is necessary to make them stop and end the destruction.
Peaceful protests are exactly that: peaceful. There is no good reason or sufficient evidence to suggest that they should be targets for violence, aggressive police tactics, or anything of that nature. If the protests begin to harm others, however, police have an obligation to protect all citizens. Regardless of the importance of the protest, if the protestors harm anyone, they ought be removed.