Just to clarify...the Confederate battle flag was introduced as a political symbol in American politics as far back as 1948 when it was widely used by the short lived Dixiecrat party, which was organized specifically in opposition civil rights and ran a slate of candidates in the 1948 Presidential election with the hope of forcing the outcome into the House of Representatives.
Not sure there is a bigger form of civil rights "protest" than to start a political party based on segregation of the races and compete in a national election.