Again I disagree, funny you said , "Civil Rights" all those pols holding on to Jim Crow and trying to deter the Civil Rights movement in the 60s were Democrats. Their ideologies change with the weather. Or whatever they think will get them elected. It's not "rooted" in anything and is far from "principled".
All those folks? That's not historically true at all. Opposition was mixed.
In 1948, when Democratic president Harry Truman ordered the desegregation of the military, many segregationists felt the Democrats had left them behind. Southern governors met together and said that if the Democrats doubled down, they would form their own party. In 1948, the Democrats chose to pick Truman to run another term and adopted a platform by liberal Hubert Humphrey (future vice president to LBJ and 1968 presidential candidate), that called for civil rights.
As a result, racist southern Democrats left the party en masse and formed their own party, the "Dixiecrats". They chose Strom Thurmond as their candidate on an officially segregationist platform and he won 4 deep south states during the presidential election in an attept to spoil the vote.
After the election the party collapsed and the coalition broke up, but for the rest of the Civil Rights movement, opponents of Civil Rights were pretty much split between Democrats and Republicans. The Republican candidate for president in 1964, Barry Goldwater, officially opposed the Civil Rights Act because he said it was "unconstitutional" to force private persons to accept Black employees and customers in their businesses. Meanwhile, the Democratic presidents JFK and LBJ had been strongly in favor of it. When the Voting Rights Act was voted on in 1965, House Democrats agreed to it 221–61, while Republicans agreed 112–24. Senate opposition was entirely in the South, which was mostly held by Democrats at the time, but those states all pretty much switched to voting for the Republican candidate (Nixon) in 1968 out of protest to Democrats supporting civil rights.
Strom Thurmond himself officially joined the Republican Party in 1964 and served as a senator for them for forty years.