What's important to note here is that in each case there was a large influx of people from a different culture who congregated in areas (think Chinatown) and took time to fully integrate into the current society. It is NORMAL for people to be apprehensive about new people from different areas who move into an area and change how things were (how the years liked it). I think it's important to be mindful of this, and not immediately start with calling those people racists, or idiots, or whatever, and recognize that a successful immigration policy must at its foundation be a slow, smooth influx, and not a shock to they system.