I guess they don’t call it Dearbornistan for nothing...
Georgia Tech tried this "Free Speech Zone" stunt a few years ago and was struck down by one brave young lady with the aid of the Alliance Defense Fund. Hers was an open-and-shut case against the university administration which banned citizens' free speech rights on its campus with the lame excuse that it still "permitted" such rights within certain designated areas. What Dearborn did at its public festival is no different, and will ultimately meet the same end.
What is different in Dearborn is that its Muslim voting bloc has reached a hardcore 30% and is steadily growing. It sounds as if the school board is already under Muslim control, at least partly. And Dearborn's elected officials are already cowed and will continue to do the Islamists' bidding out of fear for their offices and even their lives. It will require constant vigilance to protect the rights of Dearborn's non-Muslim population in the courts -- but that will be a reactive, retroactive battle. In the meantime, many Christians will leave for better places, and Muslim influence over the remaining Dhimmis will expand.
This will ultimately get bloody.