LBJ made it very clear what his intentions were, through his words to the effect that "We'll have those (Nwords) voting Democrat for 200 years".
In 1960 Richard Nixon only got 32% of the black vote. That was down from the 45% Eisenhower received in 1956. The numbers were already trending down, but Goldwater's (principled) refusal to support the 1964 CRs bill caused him to get only 6% of the black vote in 1964.
Doubtless, Goldwater would probably have lost anyway, but opposing the bill didn't help.
The question is: was Goldwater right to oppose it? Certainly, he was right to oppose a number of aspects of the bill. The senators who sneered at the idea the bill would lead to quotas and AA programs should have been thumped.
I don't think any principled conservative believes all Americans shouldn't have the same rights as other Americans. What conservatives don't like is the idea of certain groups having special rights.
Now is the time to oppose all the unconstitutional provisions of the bill. No more special i.e. unconstitutional allowances for certain groups.