Dude. Read the Constitution. Clemson still gets significant funds from the State. The Constitution is supposed to protect the free exercise of religion from State interference - including bodies funded by the State - not relegate it to a broom closet.
No constitutional right allows you to violate campus rules on disrupting classes. This is not about quiet prayer. Its about placards and megaphone where someone wants to preach. I suppose you didn't get to that point of my post.