SOUTH BEND, Indiana (Reuters) - President Barack Obama urged both sides in the abortion debate on Sunday to pursue a "fair-minded" discussion as he sought to quell a firestorm over his invitation to speak at Notre Dame, a premier U.S. Catholic university. Notre Dame's decision to confer an honorary degree on Obama and invite him to be the keynote speaker for the commencement sparked petitions and several days of protests. Some students vowed to boycott the commencement. But the speech itself drew mostly cheers, applause, standing ovations. Critics who said Obama's support for abortion rights violated Catholic Church doctrine had...