I'm not saying anything about what behavior is "acceptable" or endorsing anything. I'm saying that people and animals have been acting that way for a very long time. Tolerance for strangers is more in need of sociological explanation than the opposite. Certainly, the trend towards tolerance exists and is rising over the course of history, which I very much like. It's about asking what the default state is from which society makes "progress".
Or are you disputing the historical claim that humans on average have never been more tolerant towards strangers than today?