Complex sentence: Many claim affiliation to Ásatrú, except that the version of that religion as promoted by black metal adherents is seen as militant and fiercely patriotic or racist, treating Christianity as a foreign influence that was forcibly imposed, and therefore is a wrong to be righted.
Split into simpler sentences: Many claim affiliation to Ásatrú, except that the version of the religion as promoted by black metal adherents is militant and fiercely patriotic or racist. Christianity is seen as a foreign influence that was forcibly imposed, and therefore is a wrong to be righted.