Lest there be confusion concerning the opening paragraphs of Chapter One of TibA, I should point out that Dixiecrats were Democratic Party folk who sought to protect what they saw as the Southern way of life. In particular, they could not abide the Democratic Party's shift toward the recognition of the African American's civil rights and maintained a doggedly white supremacist outlook.
As BenG notes, Trent Lott is a typical example of the type. Raised a Democrat while it was still a white supremacist party, he changed horse to the Republican Party during the Nixon era and was elected to Congress in 1972.
Thirty years on, with Karl Rove at the peak of his powers, Lott resigned as Senate Majority Leader after being challenged for his continued support of the good 'ol white supremacist point of view.
Karl Rove is not a fundamentalist Christian. But he pushed Christian fundamentalist buttons in order to get out the Republican vote.
As far as I know, Ronald Reagan was not a white supremacist. But read up on his record and you'll be in no doubt that he pushed white supremacist buttons in order to get out the vote. That's why he went to Philadelphia, MS.
The first few paragraphs of 'Taken in by America' contain two premises of an argument; they are (i) there are white supremacist Americans and (ii) in 1980, Ronald Reagan went to what had been a hotbed of white supremacist sentiment during the Civil Rights era.
It may plausibly be argued from these premises that in order to get out the vote of America's white supremacists, Reagan played their signature tune on the dog whistle.
It cannot be plausibly argued from these premises that therefore all Southerners are inbred racist freakjs. TibA mounts no such argument.