Not similar to racial purity 

I'm having difficulty seeing the dissimilarity between those who don't like miscegenation because they are worried about "Aryans" becoming "Jewish" and those who don't like miscegeneation because they are worried about "Jews" becoming "goyim". Whatever the rights and wrongs of the views, they certainly do seem very similar. If you are arguing that in one case the distinction is racial and in the other ethnic, okay, that's reasonable, but you should note that "racial" and "ethnic" are distinctions based on the POVs in question, rather than something neutral that simply attaches to the distinction.