[md_]

Hmm, to your first part: maybe. Adam Serwer (in that same article) argues that exposure to tales of southern violence, after the Civil War, was instrumental in changing northern Republicans' willingness to push civil rights legislation. So, similarly, in the 1960s.

Yet your conclusion is far too final: it's not a "myth" that people didn't support these changes; some people did and some didn't, as with anything. At one point in the end of 1964, a majority of people oppose the protests that led to these changes.

And in fact, the 24th Amendment faced substantial opposition from southern states; I'm not able to find contemporaneous opinion polls (and I'd be interested if you have any), but it's far from the case that it was without controversy!

I strongly disagree with your last line, however—not because violence is acceptable or productive, necessarily, but because your interpretation exculpates reactionaries who regrouped and pushed back against such changes, which I think is a highly relevant lesson for the Trump era:

Race is such a good predictor of a vote for Trump. The simplest explanation for Trump's rise is that he is a counterreaction to the election of the first Black President.

So too with the success of a cynical Southern Strategy following on the heels of the Civil Rights Era.