On the contrary, what this illustrates is that there is no level of immigration that is low enough to satisfy right-wing populist demands. Right wing populists will keep stirring up anti-immigration sentiment as necessary to win elections. Actual levels of immigration, or actual evidence of the positive and negative impacts of immigration, are irrelevant.
It is rather like extremist environmentalism (by which I mean actual extremism – not just acknowledging the reality of climate change, etc.). Whatever you do, it will never be enough to satisfy the hempen-socked.