I totally agree with you guys. But it's not just in comics. In movies too! They want to make James Bond black, Moneypenny black, turned Perry White, Jimmy Olse or Nick Fury black too. I mean, I'm not a racist at all. But let's change the perspective. Could you imagine, for a single minute, Blade being white? I couldn't! Their color is part of the characters DNA.
I'm totally for ethnic or gay characters, I think they can be a great addition or I encourage diversity. But please, where did you forget your imagination? Why change what is? Put your heads out of your asses and create new characters that fit the profile! And if you don't do it because you're afraid they won't catch, then start to wonder if it's because they are black, or gay and not because they are simply poor concepts or bad storytelling.
When Stan Lee created Spider Man, it was an all new concept. Who thought a nerdy, angst you teenager could become one the best and most recognized Superhero? It was concept tough to sell at the time. But it caught, simply because the character and the storytelling were awesome.
Now, rather than changing my existing heroes, sell me a black, transgender character, and trust me, if it's good it will catch!