Breja: True equality mean that it doesn't matter.
OneFiercePuppy: Counterpoint: to a bunch of people, it does matter. So since people like you and I don't care - and perhaps don't even notice - why not change things up a bit?
Well in this case I do care, as obviously Johnny and Sue are not related in the same way they are in the comics. What impact it will have on the story, if any, I can't say yet, but it does alter thing quite a bit. Also, the actor they chose does not strike me as a choice so great it was a great casting choice regardless of race.
For example, I had no issues wit Laurence Fishburne as Perry White in Man of Steel, as that really has no impact on anything, and Fishburne is pretty much perfect for the role, so color-blind casting there made sense. And it felt as just that- color blind casting, rather than an attempt to appeal to a demographic.