Had he just reported for duty when drafted he would have served as a great inspiration for both black and white young Americans and would have been a real hero. (In addition he most likely never would have seen actual combat anyway.)
Instead he chose the Black Muslim -Malcom X- Louis Farakhan - "Hate America" path and helped to usher in the crap we see today.
If Ali had gone into the service, he would have fought exhibitions for the troops—as Joe Louis, Billy Conn, Tony Zale did during World War Two.