It's not merely a bit controversial, it's heresy
UPD: looked at your other comments... wow..
It's quite possible that high levels of immigration of unskilled or otherwise unemployable people is a bad thing for a country that shouldn't be allowed. That is a very different thing than acting like the reason it is a bad idea is because of their culture or race.
That is my problem with the whole thing, all just gets thrown into one bag "immigrants". The women assaulting islamist gets the same label as the homosexual atheist fleeing where they are in charge. (And never mind that the bible contains mostly the same bad passages as the quoran and I never done the numbers, but I assume if we count and plot "muslims killed by non non muslims vs "non muslims killed by muslims" - that number would match the felt reality)
What does "by extension" mean? Culture is voluntary. You can (and should) walk away from a flawed culture. Race is an unsheddable fixed attribute.
Meanwhile, both culture and race see more variation within groups than they do between groups, making discrimination a losing proposition even aside from its inherent immorality.
Btw, the premise underlying this fact is a fallacy. It is the norm for population groups, even meaningfully differing ones, to have "more internal variation" than between groups.
There is more variation in height within sexes than between them, but despite this there is still a very (statistically and culturally) significant difference in average height between men and women.
It's even possible for two distributions to be completely separated by a given variable while still having more internal variance.
The tallest woman is far taller than the shortest man, so if you're hiring a librarian who needs to be able to reach books on a high shelf, you still need to look at the individual.
To a limited extent as an individual. One can't simply remake the entire world they were born within.