and I think most of us in the white community have learned that. Some of course have rejected it.
I think the response for those of us who have learned the lesson that racism is wrong has been to control the definition of "racism" and make sure it doesn't include us. Racism is defined by most people in the white community as something so vile that, yeah, people are really upset by the suggestion. You've heard the rejections here of the definition used by sociologists.
This is hard work, accepting the concept of privilege, and accepting that racism is a huge societal force everyone has grown up with and is (in one way or another) affected by, rather than the work of a relatively small number of horrible people. So when you talk about racism, understanding it as a huge societal force that everyone is affected by, they hear what you say but replace it with their definition of racism - horrible people doing horrible things. So then they feel like you're calling them horrible. If you have to even discuss racism around them, the assumption is that you must feel they are akin to KKK members, and they feel personally insulted.
Second, a lot of the liberal movement comes from the labor movement. I'm a huge supporter of labor and unionization, but I have to also recognize that there is some ugly racist history in the labor movement. There are probably a reasonable number of liberals who are liberal because of their support of labor but who reject any notion of racial equality - who are just plain racist by anyone's definition. I don't know how many there are at DU, but it's certainly possible some may be here.