FFR will lose because Clemson University is not a secondary school. The faculty, administrators and students are all adults, not children. To deny the right of adults to assemble is a violation of the first amendment. If adults of their own free will wish to assemble to pray, throw frisbees, pontificate about the communist manifesto, cut each other's hair, etc., there is no authority under the constitution to deny that right. We are not talking about minors who are captive audiences in middle or high school, these are adults who can make their own decisions about where they want to be. How dare someone deny a basic constitutional right to any one of us. Could FFR be any more UN-American? Don't let the term "student" cloud this argument, these are adults we are talking about.
By the way, atheism is a belief system as well (i.e., a statement of faith). How is FFR promotion of their faith on public property any different from what they are complaining about?