Those that want to express their freedom of speech can do it outside the church and as private citizens, not members of a tax exempt institution. The minister sure as hell should keep his mouth shut on partisan politics as long as he is in his role as church leader. If he wants to speak out as private citizen Joe Schmoe, more power to him.
However to get tax exempt status, the church and its leaders committed themselves to not participating in partisan politics, etc. Seems to me that they should either stick with their agreement or give up the exemption.