DHH's fears are all feeling no fact. The "Pakistani rape gangs" targeting "white british girls" and trying to tie brown people to increasing theft is made specificly to paint brown people as dangerous. No mention of the fact that the perpetrators were all native brits, part of whom had Pakistani heritage, no mention of the fact that white people are more likely to commit child sexual assualt in general, no evidence provided for the idea that brown people commit theft. DHH is clearly associating the crimes with perpetrators at the resolution of skin color, because he does not give any other information.
A nation is not a state, it cannot be democratic. A nation is a socially constructed group identity, it's not the same as your country. A state can be multinational, as the UK is.
Racist ideology, and the very idea of races, comes from right wing ideas like nationalism and colonialism. The right wing historically supported apartheid, Jim Crow, zionism, segregation, the idea that muslims are terrorist, and that black people are criminals and dumb. There are multiple far-right groups pushing false racist narratives for decades, such as the Pioneer Fund (founded 1937) and the Human Diversity Foundation in DHH's native denmark (founded 2022). They are all far-right ethnonationalist groups.
The fact is that the nazi ideology did not disappear after WWII, it just kept out of the mainstream and tried to reinvent itself with a more seemingly scientific public image, claiming to cite statistics and banking on the audience not being able to interpret them.
The left is interested in combating these ideas, which is why it talks about them, because they are dangerous. The left does not generally use the concept of race, which is nebulous, conflating ethnicity, statehood, and cultural identity, like the protonazi Völkisch movement did.
And you usually don't sew seeds. You're thinking of stitches.