Fury, what are you talking about? They have been doing that for a loooong time now. Did you ever see the X-Men cartoon? Or how about Gargoyles? What about Batman (the one from 1992-ish, I think) which was insanely well done. Exosquad, which actually showed people dying? Or, hell, even GI Joe and Transformers. They all touched on racism, political issues (this goes double for X-Men), genocide, and dozens of other hot-button issues. ****, the greatest cartoon of all time (Looney Toons) was extremely racist and violent.
Its just that now everything either so PC that its a load of crap, that or its all XTREMEOMGWTFBBQ! just for the sake of being that way. Those cartoons I mentioned above *had* a reason to be dark, dramatic, mysterious, what have you. Not because it was cool, but because it actually fit the story.