alt Hacker NewsProtesting is basically "doing nothing, loudly." It looks virtuous but has almost zero actual affect on policy. Does any politician actually look at a protest and say "Oh, my, look at that, people don't like what I'm doing! Looks like I have to change my mind."
They never change their minds, that's because the police are willing to beat the protesters for them. The Civil Rights movement is an example of (mostly, but not always peaceful) protest that changed things within living memory. Gay rights advances in recent decades definitely owe a lot to demonstrations and public organizing that put the issues into public conversation. Women's suffrage movements also featured many protests. Policy effects are everywhere.
What has no effect pretty much ever is protesting foreign policy, because the majority of people in any country neither care nor know what happens anywhere else.