People care, because they come to the internet, or come to play games for an escape from real world stresses. People encounter racism / sexism / whatever in lots of places already, and far more frequently than you may think they do, and have this silly idea that games should be a place to for fun, free of that sort of thing.
Saying, "it's the internet" is a stupid, lazy answer, because "the internet" and "real life" aren't separate anymore. People's social lives are "the internet" plus "real life" - the artificial divide between them is collapsing, and that's a good thing. Or at least it will be once communities start putting their houses in order and policing the asshats.
That can't be done just from on high - it requires people to do more than just ignore unacceptable language, it requires normal, moderate people who don't suffer from racist / sexist etc language, to show empathy for their fellow humans and stand together with those who are hurt by it and call out the asshats whenever they do it. Make a scene of it. Get others to make a scene. Eventually the "n-word" and similar slurs will be considered unacceptable in the gaming sphere in the same way it is in most public spheres. As it should be.