Cactus, I have to say I am wondering the same thing as henry. If you are in college and approaching 21, then I am thinking you do have a right to chose your friends, unless your parents actually have some really good reasons why someone is not a good idea to hang with--i.e., a dope dealer, etc. (Over 18 is considered to be an adult, after all.) Then you could reconsider and decide.
However, if you are younger and still at home, then they might rightly have more say so. Did they say why these friends weren't the right ones for you?
Also, I am thinking you might find visiting a campus counselor helpful to get some feedback.
We aren't trying to give you a hard time, Cactus. I just want to know the circumstances, so I feel like what advice I would give is more likely to be appropriate. And I suspect henry feels the same way, although obviously I can't speak for him.