“Why did the “white people” take this sitting down?”
Normalcy bias. People expect peace at a restaurant, and think if they do nothing the problem will go away, and if they do act they will be punished. They hope that compliance alone will restore peace, fearing that stepping up will escalate the conflict.
Last night I had a comparable incident. Out for dinner, some guy was on his hands-free phone doing business loudly enough to overwhelm our conversation - even though he was on the far side of the large room. My wife was becoming distraught, but was reluctant we say anything lest he become violent. Failing to get his attention (turned out he was completely blind) I complained to a waitress, and long story short he moved and quieted down. All turned out well. Relevance? people, in public, are deeply reluctant to criticize the behavior of others in mutually polite circumstances in close proximity, fearful bad behavior well turn worse.... Yet firm calling out and request for better behavior can work, both against mistaken and deliberate disturbance.
This just drives people to avoid public places; in many cases, pure economics has less people eating out/shopping in malls anyway. These incidents just cause a few more potential customers to pack it in. The whites here were probably terrified they would end up being boiled in a pot or necklaced, and the restaurants in question are going to face an uncertain future.