Preventing flash mobs

I’ve seen and worked for restaurant owners who will ask teenagers to leave if they congregate. One former boss, whom I respected but didn’t understand, would go up to the teens and say, “This isn’t a hangout. You have to leave.” The teens were generally White, as was my boss. The teens used to complain, “Well, why do WE have to leave?” and my boss would say, “Because I told you to.” :) I used to think this was discriminatory against young people. However, seeing that he built a successful restaurant that was family-friendly, I can now see his point. There’s a reason for restaurants saying, “We reserve the right to refuse service to anyone.” It was my boss’s legal right to kick them out, and I can see why he did it.