Wait, so how is switching Blade's race problematic? Nothing about his backstory requires him to be black, so what's the issue? Why can't we have a Chris Evans, Tom Hardy, or Christian Bale as Bane? Why is casting to his race suddenly important, moreso than with a character like Johnny Storm, who will still retain his white sister in this movie?
Apparently according to you it's okay to take a white character and turn them black, but taking a black character and turning them white? Oh yeah, that's off limits. Oh, the hypocrisy...
As for Nick Fury and Electro, Nick Fury and Electro aren't Johnny Storm. They're not a member of Marvel's first superhero team, and one of the biggest superhero teams in comics. Simply put, the Fantastic Four are more important. Changing around a C-List villain like Electro doesn't matter, because Electro as a character has never really mattered much to begin with. The Fantastic Four, however, are important, and more care should be taken to get them right.
That's not to say I wouldn't have preferred a Nick Fury and Electro closer to the comics, and I wouldn't have minded an adaptation of Electro's costume either, but again, the Fantastic Four are far more important than Nick Fury and Electro. So while it does bug me, it's nowhere near as much as the casting of Johnny Storm (That and I have no interest in The Amazing Spider-Man movie series. I didn't see the first and I won't be seeing this one either).
If people want more black characters in CBM's, then great, let's see Luke Cage, Black Panther, Bishop, War Machine, Photon, Crimson Avenger, Falcon, Blue Marvel, Icon, Static, Cyborg, John Stewart, Blade, Deathlok, etc. But I don't and won't support the mangling of my favorite characters just to meet some PC quota. The Fantastic Four's been around for 50 years for good reason. So how about making an actual Fantastic Four movie instead of whatever this movie's supposed to be?