To a degree, this is true, but colleges shouldn't be in the business of favoring certain opinions over others. It strikes at the heart of their avowed mission.
I'm surprised the Jesuits didn't step in and tell the chairman of this department to pipe down.
A professor is an employee, period. Yes universities like to think they are liberated, etc.. but you are an employee.. you don't have defacto free speach on the job. Tell your boss what a jerk he is, and see how long you have a job.
You are not guaranteed employment.. you obey your boss on the job or get fired. This isn't even a debatable issue.. guys got the sign on his office, which belongs to the university and is part of his work environment... he has no inalienable right to do anything there other than what his boss allows.