In Seigenthaler's description of how the silence of race permeated America, I think that the desire for power and control combined with a fear of change accounts for the lack of voice on the issue of racial relations. Seigenthaler says as much:
I grew up in the South. A child of good and decent parents. We had [black] women who worked in our household, sometimes surrogate mothers. They were invisible women to me. I can’t believe I couldn’t see them. I don’t know where my head or heart was, I don’t know where my parents’ heads and hearts were, or my teachers’; I never heard it once from the pulpit. We were blind to the reality of racism and afraid, I guess, of change.
The silence that Seigenthaler alludes to is one in which the culture of the South was never questioned. The issue of race was never raised. In remaining silent about it, racial division was allowed to continue. Seigenthaler speaks to an almost "normal" condition. This "normalcy" is something that enabled a silence about the issue of race. It is for this reason that he speaks of not understanding the position of his parents, teachers, or himself. The silence about racial segregation enabled it to continue. It is something that was motivated by power and by a fear of change, of disrupting the reality that had governed the South for so long. In this, there is the silence present, and this silence is something that was changed by those "freedom riders."