Well, so far maybe I'm lucky, I haven't witnessed too much bad behavior on live (though, most of my time on Live has me on the original Xbox, but still).
First, I'd leave the negative feedback, as Shipwreck said, so that you aren't paired up with him anymore. Outside of that, I'd just drop it. Is it really worth it? So what, he left you a voice message, delete it and move on, or keep it and play it whenever you need a laugh. Messages like that are more of a reflection of the one leaving them than anything (and a nasty one back doesn't solve anything).
Racism, I agree, it's based on bigotry. That being said, idiot kids will use the language, if for no other reason than it makes people mad. Is it right, no. Is it really worth worrying about, no. Once again, I might leave negative feedback, but that would be the extent of it.
Really, short of someone leaving you a message saying that they know where you live, and they are coming to frag you in real life, I wouldn't put too much stock in it.