does this "republicans are racist" thing come from when historically it has pretty much always been democrats pushing racism and racist laws?

Seriously?

https://en.wikipedia.org/wiki/Southern_strategy

In the mid 1960s, a period of social turmoil, Republican Presidential candidates Senator Barry Goldwater[3][4] and Richard Nixon worked to attract southern white conservative voters to their candidacies and the Republican Party.[5] Barry Goldwater won the five formerly Confederate states of the Deep South (Alabama, Georgia, Louisiana, Mississippi, and South Carolina[6][7]) in the 1964 presidential election, but he otherwise won only in his home state of Arizona. In the 1968 presidential campaign, Nixon won Florida, South Carolina, North Carolina, Virginia, and Tennessee, all former Confederate states, contributing to the electoral realignment of white voters in some Southern states to the Republican Party. After federal civil rights legislation was gained via bipartisan votes, including the Voting Rights Act of 1965, more than 90 percent of black voters registered with the Democratic Party. The VRA provided tools to end their decades-long disenfranchisement by southern states. Hundreds of cases have been litigated to change election systems, such as at-large voting, that have prevented even significant minorities from electing candidates of their choice for city and county positions.

As the twentieth century came to a close, most white voters in the South had shifted to the Republican Party. It began to try to appeal again to black voters and rebuild the political relationship that had lasted through the 1920s, though with little success.[5] In 2005, Republican National Committee chairman Ken Mehlman formally apologized to the National Association for the Advancement of Colored People (NAACP), a national civil rights organization, for exploiting racial polarization to win elections and ignoring the black vote.[8][9]