Which Burzum album do you consider to have overtly antisemitic messages? Varg only started being a Neo-Nazi in prison and after releasing most of his influential music. So this says nothing about Darkthrone.
I was really into Darkthrone and still think they're okay, and I have nothing against any race or ethnicity.
Just one that I am aware of, and they apologized later, was their comment about "Jewish behavior".
Also, this:
Den Norrøne Rase må Slakte den andre
når blåmenn dunker for tungt på vår dør
Being concerned over it sounds like wanting to ban violent videogames, overprotective. Like hardcore Christian parents against their children listening to rock music, but maybe not as much since black metal is basically how those kinds of hardcore Christians see normal rock music.