Our capacity to justify is immensely encompassing

From Doing Bad by Doing Good: Why Humanitarian Action Fails by Christopher J. Coyne. Page 30.

The English word humanitarian can be traced back to the early nineteenth century, when the main usage referred to “those who proposed in one way or another to alleviate human suffering in general and/or advance the human race in general.” The generality of the concept meant that humanitarianism was viewed in a cosmopolitan sense, cutting across races, nationalities, and other differences among people. However, the humanitarian concept, which was drawn from a variety of religious and Enlightenment ideas, had a wide range of interpretations. Some saw the restoration of a society’s morals as a humanitarian endeavor. Others viewed charity and helping those who were worse off as central to the notion of humanitarianism. Still others extended this interpretation internationally, to include bringing civilization to the uncivilized, hence the view by some that colonization was a humanitarian endeavor.

This last interpretation led, in some instances, to the abuse of international humanitarianism for personal gain, as illustrated by King Leopold’s brutal governance of the Congo, which he justified on humanitarian grounds. As David Rieff notes, “From the beginning it [international humanitarianism] was a project that was easily misused by governments as a pretext for their own political agendas.” The man-of-the-humanitarian system view was evident even in the earliest days of state-led humanitarianism. In 1885, for example, Jules Ferry, a French politician, argued that “the superior races have a right because they have a duty as well. That duty is to civilize the inferior races.” This quotation illustrates the long-standing belief that state-led humanitarian action can shape the world according to the desires of enlightened experts who believe they are superior to those they seek to assist. In modern times, the man of the humanitarian system expresses this duty in terms of the responsibility to spread democracy, protect human rights, end extreme poverty, and rebuild better societies following natural disasters. Cases of past abuse underpin worries that modern interventions justified by humanitarian concerns or rhetoric will result in imperialism. Indeed, such concerns of “humanitarian imperialism” were recently raised by Rev. Miguel D’Escoto Brockmann and Noam Chomsky, who made reference to abuses during the colonial past before the UN General Assembly as the renewal of the Responsibility to Protect (R2P) doctrine was being debated in 2009.

One of the greatest abettors of evil is when the passion of The True Believer (Eric Hoffer) is cross-bred with the impulse to do good to others. The off-spring is pathological altruism, very occasionally beneficial, usually destructive, and always well-intentioned.

Often we look at evils of the past - massacres, enslavement, forced conversions, etc. - and we struggle to comprehend why they were not seen as evil then. Understand pathological altruism and we begin to understand why the past was not evil, just subject to the same impulses which are with us today. Our capacity to justify is immensely encompassing.