B-
Queer issues great; race, class, trans issues not as much
Carleton tries very hard to foster an acceptance of diversity; every year at freshman orientation there is mandatory diversity programming and there are college offices dedicated to intercultural and international life, and gender & sexuality. The queer community is fairly large, and the campus is very queer-friendly. As a queer woman, I feel perfectly comfortable holding hands with my significant other in public.
That being said, there is not a lot of racial diversity on campus. This means that a lot of people of color feel either ignored or tokenized and tend to hang out together. There are a good number of white allies who really care about issues of race and about confronting their own privilege. The majority, however, see themselves as "accepting" but usually get avoidant or defensive when issues of race come up. It is not likely you will hear blatantly racist remarks, but you will hear things like "that never happens here" or "that's not really an issue at Carleton".
Also, although we have a very vibrant queer community there is no trans community to speak of. There are trans students at Carleton, but they usually keep to themselves. There are lots of trans resources at the Gender and Sexuality Center, and there is usually programming about once a term centered around trans issues. But because of the small number of trans students, I think people often think that trans issues aren't as important. There has been an effort to incorporate asking preferred pronouns in group introductions, but not a lot of people have taken to the idea.
There is a wide range of class diversity among students, but on average carls are fairly wealthy. Because of this there is some unconscious classism that I have experienced. Usually if you point it out, though, people become more aware and change their behavior/assumptions.