European DNA is very genetically similar. Slavs, Celts, Germans, there might be some Jew who tries to create strife by saying slavs are subhuman, or celts are subhuman, but when you actually take a look at clusters of European DNA
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And compare them for example to African genetic clusters, or Asian genetic clusters, Europeans have the most close nit, solid connection, between eachother genetically speaking. So "Racemixing" between Europeans, isn't really a big deal. It's actually a bigger deal for a Jap to racemix with certain SEA races or certain South Africans to Racemix with east or west africans. However there's A MUCH bigger deal with dipping into other genetic clusters altogether, albeit some clusters racemixing combinations have much more positive effects than others.
Also i'm not advocating for inbreeding, but data does seem to suggest, racially similar 3rd and 4th cousins, who don't come from a lineage of inbreeding, are the most genetically compatible.