The primary reason you yourself gave was a view of "immigration issues" that is detached from the reality that Democrats have continually increased funding for CBP and ICE and increased militarization of the border with every single presidency since and including Clinton.

At the same time, your belief is that failure to enact a nativist crackdown will result in "a civil war". I thought it went without saying, but this is a very extreme view, to say the least...

The connection between nativist policy advocacy and white supremacist ideology in the US isn't new. It goes back to the very notion of "illegal immigrant"; the politician who shepherded the bill that criminalized unauthorized entry to the United States was an open an enthusiastic white supremacist who pushed this bill forward to advance his white supremacy: https://immigrationhistory.org/item/undesirable-aliens-act-o...

At the same time, this relationship is not ancient history. Indeed, nativist sentiments and white supremacist ideology are still closely linked today. See, e.g.:

https://direct.mit.edu/daed/article/150/2/40/98317/Immigrati...

> The correlation between immigration preferences and racial resentment was significant in every year. The steady correlation of 0.30 throughout the 1990s and early 2000s was impressively strong by the standards of opinion data of this sort. The rise from 0.30 to 0.50 by 2018 indicates an uncommonly strong relationship. [...] [E]very measure we have indicates that Whites' views of immigration are closely tied to their views of race.

There are many, many similar correlations between nativist beliefs and policy support and "racial conservatism", white supremacist beliefs, and Trump support (including support of Trump's extreme immigration measures).

"Racist" is not currently a label that many people in the United States are willing to openly embrace, even to themselves. It's not surprising that actual or perceived accusations of racism are received with defensiveness. But individual (and nominal) disavowal of "racism" is frankly less compelling than the entire history and presently observable empirical reality of nativism in the United States.