He walked onto the convention stage Thursday night with his wife beside him, the Constitution to guide him and the pride of a father who knows he has a story to tell.“Tonight,” said Khizr M. Khan, “we are honored to stand here as the parents of Capt. Humayun Khan, and as patriotic American Muslims with undivided loyalty to our country.”That was the beginning of a 7-minute speech that became an instant sensation—eloquent, emotional and notably original, coming as it did at the end of four days of highly processed political cliche.