Why would that be at all concerning? His grandson is guilty by blood?

From my experience guilt by blood is something that rears it's head surprisingly often even in progressive rhetoric.

For specific people but even for populations. Adjust the population a bit to one perceived to be disadvantaged in the past or bring their thoughts to a certain context and often you can trick em into essentially almost quoting these guys stopping just short of blut und boden.

Ask Marine Le Pen about her blood type as it might motivate her.