The eugenics movement in America was so consequential to world events and the history of the United States that it's a bit frightening and confusing as to how few Americans are familiar with it. The majority of American citizens have never run into the term, probably as a consequence of its absence from the average high school curricula. It is essential that all critical thinkers have a basic understanding of this movement as it grossly misused science to further racist ideology and influenced a worldwide phenomenon.
The real danger of eugenics stemmed from the fact that it gave powerful people a pseudoscientific rationale to carry out the population control programs they so desperately wanted. Under the guise of "science" state legislatures could pass laws to uphold their racist beliefs. The beginning of the 20th century in the United States was a time of great social upheaval. Many impoverished eastern European immigrants were migrating to America; their mass arrival threatened the notion of America as a purely Aryan race. The eugenics movement allowed policymakers to severely limit the influx of immigrants into the country.
While eugenics had a consequential impact in America, it also had implications for other scientific communities as well. Some of the main proponents of eugenics in America were in correspondence with and gave advice to Adolf Hitler. It's unlikely the Third Reich would have been as successful at its aims as it was without the example set forth by the American eugenics movement.
Discussing eugenics raises some interesting questions regarding power. Who should have influence over public policy in America? What factors should be considered when deciding rights such as voting or even birth control? Being ambivalent towards issues of this sort can lead to disastrous results.