Due to some legal guidelines college campuses have to have free speech spaces where anybody can setup without any notice or authorization and the university can't do anything about it unless it's harmful speech.

We all might think that what they're spewing is harmful but the preacher's gaggles of lawyers have won a lot of arguments saying otherwise.

I believe the 3 zones at MSU are the green triangle behind the PSU, the brick bear head mosaic in front of the fountain, and the stage infront of Strong hall.