Obviously, this is a controversial subject. Yes, some racist comments have been made in this thread. Most were mild to insensitive or inappropriate. But those comments were made by a very small minority of users who have consistently said offensive things on a broad variety of subjects. That small, offensive minority doesn't represent MAP in any way. Most are probably fairly obtuse individuals who don't realize they are silently tolerated here for no reason other than their failure to sufficiently violate the ToS. But the communities unwillingness to call them out more vocally might have more to do with the individuals making those statements. Some people here might feel it's unproductive to follow those users through every off-topic discussion and vocalize every disagreement they have with them simply because that would be the majority of their posts and it might be seen as adversarial to the mods. So it becomes more of a, "oh, great, so-and-so said another stupid, insensitive thing today. I won't bother to reply to it. The attention only seems to encourage him/her anyway." That's not the same thing as a silently racist community who isn't offended by those comments.
Try to remember that most of MAP is pretty liberal, well-educated, traveled, and culturally diverse. I seriously doubt the vast majority of users here are remotely racist. Do they occasionally still have insensitive, bigoted thoughts? Yup. Pretty much everyone does. Most just do a good enough job at self-filtering so they don't vocalize those thoughts.
One of the primary reasons I enjoy being part of MAP is because the mods here vote on how behavior applies to the rules, not on their personal feelings about the subject. I think they do a pretty exceptional job at that. One drawback to that system is that people who only ever say borderline offensive statements without going too extreme become entrenched and ultimately semi-tolerated. They're here so long as they don't mess up big time, so most people just kinda ignore them and hope they go away. Considering what a small minority of MAP they represent, it's not usually a very big deal.
Now, some insensitive/racist comments aside, if you just examine the evidence in this case, I think there is nothing that supports that Zimmerman was racially motivated in his actions. You can't demand the public be outraged about a subject when the local police and FBI investigate and not only cannot find any evidence of Zimmerman being racist, but actually find ample evidence that suggests he wasn't racist and was very warm and welcoming with many black members of his community. Is it a tragedy that a young kid died over something this stupid? Yes. Was it racially motivated? No. That doesn't mean that institutionalized racism doesn't exist and needs to still be changed. It means it doesn't apply in this one case despite how much some people seem to want it to. So don't give up on people because they're not passionate about this one topic were no evidence of racism was found. Focus your energy on drawing attention to legitimate racism and try to ignore this media fabricated sort in the future I say.