There was an assumption of the inequality of the races and acceptance of slavery on that basis. That's probably what was meant by "those values".
For the regressions, and continuing with my previous assumption: President Trump has been soft on some of the white supremacist groups, for example, being slow to disavow the support of those groups' leaders. This has emboldened some racists to be bolder. Previously, in places like California, racism almost seemed like a thing of a bygone era (at least, it wasn't as overt).
But 1850's American culture is distasteful to me and also to sullyj3 as they say:
"it's manifestly obvious that modern American culture is superior to American culture of the 1850s"