The durability of demographic panic as a way of promoting racism is absolutely a phenomenon (I'm not saying that was your intention Gob). Americans, different groups, have used it to focus fear and hatred on many minorities, Jews, Irish, Italians, Catholics in general, "immigrants", Mexicans, Chinese &c. And it is popular internationally as well. Part of the motive for genocide against the Rohingya (sp?) is the false belief that they will out-breed and displace Buddhists. The hard right in Israel has promoted the idea that Palestinians (both Christian and Muslim) will displace Jews and used it to get approval for policies which force non-Jews out of Jerusalem which are narrowly legal but harmful in intent. ( In spite of the evidence that it is the ultra-orthodox who outbreed nearly everyone)
The GOP has worked hard pumping fear of all immigrants using this same meme for 30 years and it was a big part of the irrational fear driving Brexit.
There are several problems with this. The first is assimilation, which goes both ways. The longer people live in contact with each other the more they become like each other and the less they are seen as "other, scary, alien". one Historian of China said that the miracle of the Middle Kingdom was that after each wave of Mongol invasion and conquest the Mongols became gradually sinisized, they became Chinese, so when the next Mongol invasion came they WERE Chinese. There are a few examples of communities who have kept themselves apart from the larger world. In the US they have been Hutterites, Amish, Ultra-orthodox Jews, But a feature of being successfully separate is they learn how to 'keep the peace' between their communities and the larger society and are thus harmless.
Another problem is that they get the demographics wrong, nearly always.
https://www.theatlantic.com/internation ... th/545318/ In the US it is true that first-generation immigrants have larger families second and third generations become more like the surrounding community because they are influenced by the same economic and social pressures which controlled their birth rate. This is longish but describes the transition starting in the late 18th century to the present in reducing parity it is one of the most interesting things I have read in two years:
https://theviewfromhellyes.wordpress.co ... -memeplex/ And it details how both Mormon and Roman Catholic birth rates have rapidly shifted towards the community averages.
And the final problem is that it all begins with a subtle lie. It asserts difference between human beings who are really a lot more alike than different. But it is the assertion of difference which creates the foundation for oppression and brutality. We only OWN our own personal histories. The history of our nations and tribes belongs to everyone equally as both warning and aspiration.
But fear is a powerful tool for manipulating people and "fear of the other" is deeply rooted in the most primitive parts of human brains so I don't think it will go away.
yrs,
rubato