R is not for Racist

Just for your info the republicans voted unanimously for every civil rights act but the 1964 act, and still had a majority for the 1964 act but had less support because they didn't like the government determining who companies could hire.
Let's examine the other years as well, Nixon won just about the whole country in 72 so saying the south turned republican is difficult when the whole country did as well. The same can be said of Reagan in 80 and 84 and Bush in 88. So there is no republican bias in the south in presidential elections until the last 4 presidential elections. I doubt you are claiming that it took 30 years before the effects of one civil rights act caused a shift.
Now let's look at the senate ejections. 1964 was demicratic sweep, 1966 was handily won by democrats. 1968 was a sweep by democrats. 70 went to democrats, 72 the south elected democrats, 74 again democrats, 76 democrats, 78 was split with the deep south going democrat. 80 was the 1st time republicans won the south. In 82 democrats won the senate elections in the south. 84 was split with democrats edging out republicans, 86 was a sweep for the democrats, 88 was split, 90 was split with the deep south going democrat, 92 the democrats won the south.
The republicans don't start consistently winning the south until the mid to late 90's. If anything you could claim it wasn't until the racists southerners started dying off that republicans had a chance in the south.