I wonder how MacArthur would influence the Civil Rights Movement. For what ever his other flaws, he was a strong proponent of desegregating the military.
I think it would be more accurate to say MacArthur was pretty apathetic on the subject of desegregating the military on his watch. It wasn't a hill he was willing to die on, but he wasn't going to help the process along either. Two years after Truman's historic order, and yet not one unit of the Army in the Far East Command had been integrated. Unofficial integration of Eighth Army didn't begin until late in 1950, and it was not until after MacArthur's recall the following year that his successor Matthew Ridgway began to desegregate the command. Never forget that when you tolerate a virulent racist like Ned Almond as your Chief of Staff-a guy who went to his grave advocating for a segregated military, and doing everything possible (*) to prevent integration-it's pretty safe to assume that whatever lip service you give to the subject of civil rights is just that-lip service. To be fair about it, Mac wasn't alone in that attitude-his military peers like Eisenhower, Marshall and Bradley weren't much better on the issue-but the reality seems to be that it was a moral challenge he was content to pass on to a younger generation.
(*) To quote an example, in one of his last official acts before his untimely death, Walton Walker, Commanding General of the Eighth Army, recommended that his command be desegregated. Ned Almond, in what was one of HIS last official acts as Mac's Chief of Staff, recommended that Walker's proposal be ignored, and so it was, until Ridgway decided otherwise.