In otl Goldwater opposed the Civil Rights Act.
Goldwater voted against the
1964 Civil Rights Act (there were others). His claim was that he regarded the Act's clause regarding discrimination by private businesses as unconstitutional overreaching, but had no quarrel with the rest of act. This is plausible, as Goldwater had a strong libertarian streak, and other libertarians made similar arguments.
However, there is also evidence that Goldwater was making a conscious pander to segregationist white Southerners, who seemed ripe to bolt from their traditional loyalty to the Democratic Party.
He seems not to have been personally racist...
Goldwater was a long-time member of the NAACP. His family's department stores in Arizona were desegregated, and as commander of the Arizona Air National Guard, he carried out its desegregation.
but his approach linked him in many minds to some very unpleasant folk
He appeared to be pandering to racist white Southerners.
WI he had run with Ed Brook as his running mate, assuming Brook had won some worthwhile office before then
Why assume anything? One can look up Brooke's career in 30 seconds at the
Congressional Biographical Dictionary.
But it is not a plausible suggestion. In 1964, Brooke was running for re-election as Attorney General of Massachusetts. He had no national standing and would not have been a plausible VP nominee. Nor would he have accepted the nomination (IMO) since he would have been offended by Goldwater's pandering vote on the CRA, would not want to serve as a token to cover Goldwater's fault, and would not want to give up his office to join a kamikaze campaign. (Goldwater was doomed on several different issues, including foreign policy and Social Security.)