The Iraq War protests were some of the largest in history, and they accomplished exactly nothing (and to your example, look up Malachi Ritscher). Occupy Wall Street was a massive movement and accomplished nothing. The protests against Obamacare repeal were massive and widespread, and seem to have only succeeded in delaying the destruction of Obamacare to the current tax bill. Black Lives Matter is a massive movement that has accomplished meaningful change in a few jurisdictions and nationwide has managed to at least generate conversation, but that conversation has already been largely derailed to the question of whether or not football players need to stand for the national anthem.
Office holders are not beholden to people yelling in the streets but to the people who get them elected. This means the people who show up to vote and, increasingly, the people who finance their campaigns.
That's completely incorrect, the easiest thing in politics is to get people to vote for you, especially in a two-party system that effectively prevents challengers to the status quo in an election. All in all, the only power that people effectively have is the power to revolt. Democracy is a peaceful system of government but it can only be maintained through the threat of revolution. When that threat doesn't exist, politicians will do whatever they want.
The act you describe at the end of your post happened in a dictatorship where the people truly had no voice. While we may live in a flawed democracy[1] we're not in the same situation -- we do still have nonviolent ways we can turn things around.
Things haven't reached that point, but will soon.
Yes, ultimately it failed, but it is difficult to dispute that it was a noble attempt. More will come in time.
Unrest in this part of the world will continue as the population is still rising fast, average age is very low so you get young unemployed population with no jobs and no money and basics such as food are rising in price. That is a recipe for more revolutions.
But revolutions and overthrowing of local governments won’t solve the underlying issues of these countries not being able to provide some reasonable standard of living to their population due to economic reasons.
It would be much safer to do incremental change and try to slowly build up local economies to create jobs for millions of young people. Violent revolutions will only further damage economic conditions and make situation worse in many cases.
The Internet, despite its tremendous potential, has proven to be a massive liability, as it gives people the illusion that they have done something useful and constructive after they post angry comments on message boards such as this one. At the end of the day though the truth is this: political representatives will only really represent the populace if they are constantly worried about real backlash, such as if hundreds of people are gathered outside their office blocking access to vehicles, buildings, and so on.
On December 17th, 2010, Mohamed Bouazizi famously set himself on fire, which precipitated the Tunisian Revolution and the wider Arab Spring. At this rate, America is going to need equally brave and selfless individuals to make a stand and spark similar movements.