I guess public institutions do have to advertise religious events:
Wisconsin Library Finally Allows Posting of Pro-life Event FlyerGood news for all of us. Now we can count on Liberty University to defend library flyers posted by socially conscious Lutherans who want to schedule prayer vigils outside anti-tax seminars, and maybe even a Muslim students alliance that wants to protest racial profiling outside Mitchell International Airport.
West Bend, WI (Lifenews.com) -- After the pro-life law firm Liberty Counsel intervened on behalf of a West Bend, Wisconsin resident, a library director agreed to allow a flyer announcing a pro-life event to be posted in the library along with other community announcements. Mary Weigand wanted to inform others about an annual Life Chain event, but the library director refused to allow the flyer and insisted that the library policy prohibited religious material. Weigand contacted Liberty Counsel. After receiving Liberty Counsel's demand letter, the library director apologized to her and allowed the flyer to be posted on two library bulletin boards in time for the event. Mathew D. Staver, Founder of Liberty Counsel and Dean of Liberty University School of Law, commented, "When libraries or other government facilities create an open forum such as a community bulletin board, it is impermissible to discriminate against religious viewpoints."
Unless, in America, some animals are more equal than others.
[whew... did I actually need to add that link?]