I don't think they did say any of this. I don't understand why people who debate against limiting immigration (and it often is only this way round) continually mis-represent the person's clear, stated concern and try and replace it. It is a completely transparent attempt, and no one is fooled. This isn't 2015 when an accusation of racism was taken seriously, because who would mis-accuse someone of such an awful thing? Well, it turned out millions of people would do that. The US President would do it[0].
As for the genetics comment, this is ridiculous on its face as well. Race and culture are in no way tied. But culture survives for many generations, particularly when the immigrating group is large enough. This is obvious. Germans in the 1900s could move almost anywhere in the world and become the best brewers in the region, not because they have the genotype of a brewer, but because they had (and still have) an incredible brewing tradition handed down from parent to child. Culture doesn't change because you move into another country. It moves because you assimilate, make lots of native friends, and learn the language. Lots and lots of people are not doing that.
[0] https://www.nbcnews.com/news/us-news/kyle-rittenhouses-mothe...