Riots don't necessarily need to achieve an objective. It creates a political and economical cost to politicians. It means that you can't simply ignore the minority only because you currently have a majority, so it forces them to consider a compromise good enough. That's not always possible but it's essentially what separates France from Turkey. In Turkey, Erdogan wins the elections by %51 and completely ignores the %49 because they can't win an election and can't disrupt the public anymore.
>You are naive if you think Europeans have any semblance of control
Who do you think has control?