Yes, they fought against slavery. But after that, what did they do? Racism was not the exclusive problem of the South. There was and is racism in the North too. It is just expressed differently.
I watched this video very carefully, then I looked into the facts the video did not mention.
The video talks about who won elections in the South and the in the North, assuming that South=racist and North=pure as the driven snow. They try desperately to show the Republicans as standing for non-racist values and the Democrats being consistently racist. But the real question is, what do Democrats and Republicans believe?
To answer this question it is instructive to look at the vote for the 1964 Civil Rights Act. As this history shows, be vote went like this:
The original House version:
Southern Democrats: 7–87 (7–93%)
Southern Republicans: 0–10 (0–100%)
Northern Democrats: 145–9 (94–6%)
Northern Republicans: 138–24 (85–15%)
The Senate version:
Southern Democrats: 1–20 (5–95%) (only Ralph Yarborough of Texas voted in favor)
Southern Republicans: 0–1 (0–100%) (John Tower of Texas)
Northern Democrats: 45–1 (98–2%) (only Robert Byrd of West Virginia voted against)
Northern Republicans: 27–5 (84–16%)
As we see, the few Republicans in the South voted unanimously against the bill. And in the North the support among Democrats was slightly stronger than the support among Republicans. Both parties in the North were generally supportive. So if Republicans had always been on the forefront of fighting racism, they did not show it any more than the Democrats.