It’s a commonplace that humanism, and especially secular humanism, “punches above its weight." Our movement has never been more than a minuscule minority phenomenon, yet humanists (as well as historic activists we would now recognize as humanists even if they did not know the term) have played an outsize role in promoting some of their eras’ most prominent social reforms.
Consider one example from the nineteenth century. Popular historic discourse today tends to spotlight religious activists and clergypersons who agitated for the abolition of slavery early on, when abolitionism was unpopular even in the North. Doing so not only distorts the true numbers of clergy and churchgoers who used their Christianity to defend or simply tolerate slavery; it effectively buries the contributions of indispensable early antislavery activists who were either irreligious or wildly religiously heterodox. For example, many were radical Quakers (such as the Hicksites), whose doctrinal views might not be out of place in religious Humanist congregations today. This same group provided much of the early impetus for the woman suffrage movement, whose debt to explicit freethinkers such as Elizabeth Cady Stanton and Matilda Joslyn Gage went underappreciated for many decades.