Prison officials violated the First Amendment when they punished an inmate for writing a profanity-filled letter to then-Gov. Patrick J. Quinn, a federal judge ruled.In a written opinion this week, Chief U.S. District Judge Ruben Castillo conceded Fabian Santiago’s letter complaining about alleged corruption within the Illinois Department of Corrections was “unnecessarily rude and derogatory.”Castillo also conceded prisons may put restrictions on outgoing mail.But such restrictions may be imposed only to …