What makes it more outlandish is that there were no teams in the South unless you count St. Louis as "Southern." It was mainly Northeast and Midwest cities that had teams.
There were quite a few southern ballplayers in the majors...they were probably most of the 20% who didn't want to play with blacks.
In 1962 the state of Mississippi still had laws against whites playing with blacks. When Mississippi St. qualifed for the NCAA basketball tournament that year the coach, Babe McCarthy, had to sneak the team out of the state to play.
The thing is when Jackie Robinson was going to play in the majors a number of southern ballplayers (Dixie Walker and some others) protested that they were upset about that. They threatened to hold out.
The commissioner, Happy Chandler, told them in no uncertain terms that if they held out, they'd be banned from baseball. The protests stopped. Happy Chandler was a Southerner.
I think most Americans realized it was the right thing to do. Too bad it didn't happen a lot sooner.