Pretty much the whole political range from the extreme Right up to and including the Greens (but not the Left party) normalized racial discrimination with their whole "unwavering support of the Jewish nation" (i.e. unlimited support entirely because of their race) whilst they mass murdered civilians because of their ethnicity (a crime so foul that the list of dead Palestinian babies 1 year old or younger for the first 6 months of the Genocide is 17 pages long).
They not just normalized in Germany the mindset of discriminating on the basis of race, but once the Genocide started they went all the way to unwaveringly supporting a modern variant of Nazism giving as reason for that that those doing it represented "the Jewish People".
It's absolutely natural that the Far Right nationalists would think that "well, if even mass murdering Palestinian babies is fine if the murderers are Jews, then surely it's equally fair that those who are Germans should be able to do whatever one wants to non-Germans" (or in other words "if it's fine for them, then it's fine for us too")
There really isn't that much of an Ethical and Moral distance between "those of a specific race can mass murder babies of the ethnicity they deem 'human animals'" (which is what almost the entirety of the German political class defended) and "our specific race can treat other races any way they see fit" (which is the AfD's position) - in fact I would even go as far as saying that "merely" being anti-Immigration is Ethically and Morally a less monstrous position to hold than supporting mass murder of innocent civilians because they're from a different ethnicity than a race you favor.