The majority of leading DEMs and especially those in the South were violently opposed to Truman's stated civil rights positions.
VP Henry Wallace ('41-'45) is an example of the DEMs even then... he would have been POTUS if he had remained VP in 1944 with FDR's pending death. Wallace ran against Truman in '48 on three major issues; Turn our nukes over to the United Nations, nationalize all the railroads and coal mines, and provide huge reconstruction funding for the Soviet Union.
Just few points from McCullough's book Truman.
Harry bears little resemblance to today's DEM traitors.
Henry Wallace was a Communist. He was considered a major liability to the ticket and it was why he was demoted to Agriculture Secretary.