Much ado about nothing. When I first saw this, I must admit, I did have an incredulous reaction -- these are Norse gods, after all. However, here's how you could explain it, if you must.
As I recall, in Norse mythology, there were two sets of gods, the Aesir and the Vanir. Now, it's true the Vanir are depicted as fair, but I also recall that the death goddess Hela's body is half black. Maybe Heimdall is a Vanir.
Now, perhaps it's possible that the Norse gods, while worshipped by fair-skinned people, might have a broader color palette, but can appear as white to those who worship them to make them feel comfortable. After all, the Hindu gods are represented with different color skin (blue, for example).
I also recall there were light elves and dark elves. Is it truly beyond the realm of possibility that in a mythical kingdom like Asgard there could, figuratively speaking, be "light" gods and "dark" gods?
I know I'm reaching, but hey, I think you can justify anything. (I was developing a character based on the Incan gods, and had the idea they were all a different, non-human color, like gold, but were able to appear to humans to have ordinary human hues.)
The fact Dusty
are all bent out of shape about this actually pleases me, and I think TPTB make casting decisions like this to piss people off and get them talking about their projects.
Now, it would have been preferable for a film about Norse gods to cast more Nordic looking folks -- but I'm sure several of the white actors who will be cast in the roles aren't exactly Nordic. Some will have -- gasp -- brown hair and brown eyes!
Also, look at Kevin Sorbo from the Hercules TV show. He's not Greek, yet played a Greek demi-god.
I also recall some gasps when George Perez worked on Wonder Woman in the '80s and he had the nerve to draw -- gasp -- black Amazon sisters of Princess Diana! Oh, teh noes!