Is cockblocking ok, sometimes?

My roommate occasionally returns to the room with what we have dubbed 'the skank parade'. pretty self explanatory, it is a group of slutty dressed girls that are taking advantage of him by drinking his alcohol. I understand that i have to let him get anything he can, but it has become imposing on me. sometimes they come home extremely late and the girls are so trashy that i feel uncomfortable brining girls home with me or even having friends over. at some time, is it ok for me to tell him stop, or even further, to just be so rude that they dont want to return?