Who were against the Eugenics program? Why did they claim it was a false science?

In 1910, an equilibrium model was created by Godfrey N. Hardy and Wilhelm Weinberg, which disproved claims from the Eugenics program, developed by Francis Galton in the early 1900's, that low-class families were "tainting" the gene pool with dysgenic genes.

Later in 1935, the Carnegie Institution disproved the majority of the Eugenics Record Office's work of any scientific merit based on the works of scientists such as George Shull, who showed that hybrid organisms were more vigorous than pure-breed ones, thus discrediting racial purity as biological superiority.