There's a decent mix of people on campus. If you really want to find people with a common ethnicity, then there are culture clubs. I have been the only Black person in most of my classes, but that can be caused by a lot of things. It might be that there aren't a lot of African Americans with a Human Services and International Affairs dual major. Who knows? Regardless, I always feel respected in classes and on campus.
As for the economic background, I feel that a lot of students are from upper middle class or just plain wealthy families. I have to admit that sometimes it's a little overwhelming to be around privileged students when I'm barely making rent and struggling to pay the tuition.
I'd say that most students on campus are pretty liberal about religion and sexual orientation. I think Northeastern has made a great effort to make students of the GBLT community feel welcome / comfortable. The college honchos are starting to use gender neutral pronouns on applications.
For political beliefs - I think students are very passionate about their beliefs. I think there is an expectation for young students to be liberal in their views. On a scale of 1-10, I'd say political tolerance is a 7.