The idea of Scientific Racism began to be rejected during the mid-twentieth century. A fair amount of this does have to do with the Holocaust and the stigma that became attached to Eugenics. What was seen was a shift in thought as the idea of the "Culture of Poverty" became the more popular theory to explain the condition of minorities in America, specifically the Black and Latino communities. The Civil Rights Act embraced this argument and a lot of its efforts went into fixing what were identified as problems within minority households that originated not from their race which was their birthright, but from the poverty that they came from and were born into. To put it simply, the new culture of poverty argument asserted that their time in poverty led the Black and Latino communities to develop tendencies that became ingrained into their culture and were detrimental to their success such as laziness, broken households (absentee fathers etc.), a weak desire for education, and a general lack of education. A couple good books, if you're interested, to read are Ethnic America: A History by Thomas Sowell which largely supports the Culture of Poverty argument in his telling of the history and development of the various ethnic groups that have made their way into America. Another book is The Ethnic Myth: Race, Ethnicity, and Class in America by Stephen Steinberg. In this book Steinberg refutes the Culture of Poverty argument and argues that the issues facing minorities in America are more social than cultural. Both books are very interesting and informative reads.

In some cases it was not rejected. There's a vague notion of reformed and unreformed professionals, denoting those who cling to the intellectual heritage of scientific racism and those who do not. In the anthropological community, this can sometimes crop up as an issue. Folks like James Chatters continue to operate on antiquated ideas of race. Also, consider the thinly veiled acceptance and respect that issued from surprising places after the publishing of The Bell Curve.

The embattled, but continued currency of this thinking trickles down to the layman, too. As a university student, I can't remember how many times I've witnessed some white dude regurgitating cute factoids about the lower average intelligence of black men and women. Usually as a justification for their "rampant criminality". Sometimes it is from the most (seemingly) unlikely people, like an old friend from highschool, or a fellow grad student. The point of the perpetuation of scientific racism is that it allows people outside of academia to cite the bullshit, and use it as leverage in some very active racism.