The Tories want to turn us against migrants by dividing people between 'us' and 'them'; well, let me tell you about another bunch of guys who believed in 'us' and 'them' - the Nazis. Radio presenter James O'Brien made near enough this exact parallel when he quoted from Mein Kampf to show the eerie similarities between Amber Rudd's speech and the former German chancellor's words.
Of course, Mr O'Brien didn't need to quote Hitler. He could have cited the former Labour leader, Ed Miliband, who had the same idea; he might be a less famous figure, but he's marginally more relevant to British politics in 2016. Or instead of reminding us of Nazi Germany as a precedent, Mr O'Brien - or any of the hundreds and thousands of people referencing the Third Reich - could have cited the USA, which already publishes data on H1B visa reports.
I'm not sure how useful such information would be; companies that excel in poor wages and working conditions will most likely have a large number of overseas workers, but so too will very highly skilled, elite firms. Immigrants tend to be disproportionately represented at both extremes in employment (as they are in every other measure, whether it's wealth, educational outcomes etc etc).
But the collective hysteria that followed shows what happens when Nazi Germany crowds out all other history. The poverty of peoples' collective memory and imagination is such that the first minute any politician strays from the path of universalism, commentators reach for the most shocking (and only) historical comparison they can think of.
What has simply happened, as often happens in history, is that a progressive idea has overstretched itself and run out of steam, and the tide is coming back in. History is full of examples of society becoming more conservative; it did so in the 11th and 12th century with regards to sex and marriage, and once again in the mid-19th century; outside of the West most of the world is becoming far less liberal right now. Tony Blair's time was the high-point of universalism in Britain but it has peaked and failed to break out of its core support.
Maybe people find this hard to grasp because they're so used to seeing history as a linear structure in which we're all heading off to the glorious future - because progressivism is on the 'Right Side of History'. Like many things, this idea comes from the two most influential belief systems of our age, Christianity and Marxism. Much of the anger post-Brexit stems from people tasting defeat for the first time, having assumed they would always win the progressive fight.
Likewise there is the assumption that as Britain becomes more cosmopolitan and diverse it will become more tolerant and liberal; setting aside the fact that immigrants are not the ciphers many would like them to be, it's just as likely that tolerance is shaped like a bell curve, and that after a particular point more diversity leads to less of it.
When the Prime Minister says that: 'If you are a citizen of the world, you are a citizen of nowhere,' she is paraphrasing Pierre-Joseph Proudhon, who stated that 'if the whole world is my brother, then I have no brother'. This is the language of particularism. There is no right answer to this, just two different visions of the world; on the one hand those who prefer the comfort and stability of people like themselves, and on the other those who prefer the sensation and openness of diversity and churn, the mixture of languages and cuisines and fashions.
The latter group are heavily found among the creative classes and the well-educated, and so wield disproportionate power; they were almost uncontested for many years but despite this have never converted more than at most a quarter of the population, and probably never will. (A quarter of the population in western Europe. Outside of the West the proportion of globalists is in single figures, if not a matter of decimal places). And when an idea fails to break a certain threshold then it is clear it has run out of steam.
Immigration concerns are mostly not about economics. It just suits both sides to use this as a proxy debate for the far more troubling social issues, namely the natural human affinity for living around people like ourselves. This doesn't make you Hitler - just a human being.