A code of ethics.
Cultural relativism has been proven to be nonexistant concerning ethical matters, nearly every culture in the world has taken the same base values to the core regarding human dignity.
Those born into a higher class can mindlessly accept their social circumstances, and perpetuate what is taught them (terrorists accepting support from their peers and being seen as heroes by a certain community), or they can iterate on the status quo by combining their experiences with reason.
These powerful men made a realization about the potential of a human being through the combination of deep thought, immersion in literature and/or personal experiences.
They recognized the value of human wellbeing and happiness that outweighed the repercussions of challenging the standard, while also being in a position of power where they were able to fight against the norm.
Next to being exemplary human beings (you would need to be prolific in many fields to become a revolutionary) they also all display a strong adherence to a certain morality, which drives them and their actions.
I myself do not agree with their views, nor the means through which they tried to accomplish these, yet I don't think anyone is able to say that these leaders were not commendable and exemplary men in nearly every facet of their being.