How did social reformers in the progressive era contrast with the beliefs of social darwinists?

Many people in the progressive era used Social Darwinism to modify the social and political measures, like the justification of imperialism, anti-immigration policy and favor of free trade. They believed that government should not intervene in the socialist welfare scheme which hindered the process of natural selection and survival of the fittest. However, the progressive era witnessed the change in this attitude and people who made these claims could not stand in the era of industrialization, urbanization and a new social society which is to be governed by laws.