Not sure I believe that for a minute. There's definitely a group there, nobody can deny that, but Norse mythology is incredibly popular among leftists too - I say this as somewhat of a Norse mythology leftist, whose favorite viking/odinist/pagan band preaches unity and kindness among all people and is fronted by a polyamorous bisexual - there's a lot to love in the mythos and the factual history, and it appeals to a wide variety of people for a wide variety of reasons.