Forgotten War Hero Hugh Thompson Prevented the Genocide of 20,000 in My Lai Massacre

What makes one person prevent genocide and others participate in it?" Professor Robert Sapolsky lectures/writes if we are not to repeat history, we should study the hero who stopped the genocide not those who caused it.
For him, Hugh Thompson, from the Viet Nam era stands out above mostly all. There comes a moment for the hero when there is no more "us and them". The crisis of the moment allows for no discrimination. Hugh Thompson, (now a decorated war hero), stopped the continuation My Lai Massacre and perhaps even the genocide of 20,000 more. "One of the things that helped galvanize the anti-war movement", says Sapolsky, "was the My Lai massacre".
In, "Behave: The Biology of Humans at Our Best and Worst" Robet Sapolsky, says we should prevent ourselves from repeating genocidal history by studying the lives of those who stopped atrocities from continuing. Hugh Thompson stands out to him in human history where humanity kicks in to save lives no matter the personal sacrifice. This type of potential in human bravery should be studied and remembered.
"Why do we do the things we do? Over a decade in the making, this game-changing book is Robert Sapolsky's genre-shattering attempt to answer that question as fully as perhaps only he could, looking at it from every angle. Sapolsky builds on this understanding to wrestle with some of our deepest and thorniest questions relating to tribalism and xenophobia, hierarchy and competition, morality and free will, and war and peace. Wise, humane, often very funny, "Behave" is a towering achievement, powerfully humanizing, and downright heroic in its own right"--