Stephen Pinker makes a similar point in The Better Angels of Our Nature: Why Violence Has Declined (2011).
Research suggests that as frequency declines, perceptions change but not in the way that might be expected. As frequency declines, the boundaries of concepts expand relatively rather than registering the absolute decline, as a measuring instrument would do. So it can appear relatively that the phenomenon is reaming the same or even increasing, when it is actually decreasing.
While racism, sexism, and violence are actually moderating — there are no longer any lynchings in the US, for example — it appears to many that things are getting worse.
This is not to diminish these on-going social problems that still plague many individuals, but some progress is being made socially and that cultural change has been reflect in law.
"You've come a long way, baby." But there is still a long slot to go, especially globally, especially where progress has been very uneven or non-existent.
Liberalism has had an effect.
Marginal Revolution
Why Sexism and Racism Never Diminish–Even When Everyone Becomes Less Sexist and Racist
Alex Tabarrok | Bartley J. Madden Chair in Economics at the Mercatus Center and Professor of Economics at George Mason University, and a research fellow with the Mercatus Center
Marginal Revolution
Why Sexism and Racism Never Diminish–Even When Everyone Becomes Less Sexist and Racist
Alex Tabarrok | Bartley J. Madden Chair in Economics at the Mercatus Center and Professor of Economics at George Mason University, and a research fellow with the Mercatus Center