There were many white Americans fighting for equality for all. Heck, look at the recent BLM movement, the woke discussions, #metoo and more.
All of these things were possible because of the 60s, because of white legislators, white judges, white supreme court judges, pushing for change, enacting change, creating the US today which, while imperfect, is quite supportive of equality, both legally and culturally.
So yes, there was all sorts of main stream media pushing for equality.
Heck, the first interracial kiss on US primetime was in the 60s on Star Trek ToS.
Some examples of racism were documented in some progressive outlets, therefore all examples of racism would have made it into the public record?
Maybe there was concern, when progressives were fighting this sort of thing, that if they picked the most unbelievable example, the naive public (those not familiar with the residents of a typical Klan-era backwater Louisiana parish) would question its veracity… as we see today…
Imagine you were going to forge a such a test? I don’t think I could make up something this ridiculous if I tried. I’d have to be practiced in generating trick questions, and motivated by malice to come close. Realistically, I’d give up and pick one of the readily-available real examples of poll tests to use.