I feel like I should have lots to say about the spreading violence, but I don't really.
It does rather show why open borders wouldn't work so well. It's got less to do with the actual effects of immigration on wages or anything and more to do with the fact that people simply won't stand for it. But this is simply a fact of the world as it currently is, not and argument for the inherent justice of tight border controls. There are plenty of cases where just action will spur violence, getting rid of apartheid and slavery are obvious examples. Often it's smart to stop short of demanding a satisfying conclusion to the injustice to prevent widespread violence. Whites here were mostly left alone and we kept our land and most countries compensated slave owners when slavery was abolished (America was the only country that didn't and that did involve a staggering amount of violence).
So, sure, whatever, just don't think that the foreigners going home is going to help anyone. It may help to stop a decent into violence but don't expect it to address any of the issues that started the trouble in the first place.