If a lot of people with incompatible interests all claim that right is on their side, how do you decide between them? In a paragraph of the final part of The Communists and Peace, Sartre had sketched the outline of a bold solution: why not decide every situation by asking how it looks to "the eyes of the least favored", or to "those treated the most unjustly"? You just need to work out who was most oppressed and disadvantaged in the situation, and then adopt their version of events as the right one. Their view can be considered the criterion for truth itself: the way of establishing "man and society as they truly are". If something is not true in the eyes of the least favored, says Sartre, then it is not true.
...This is similar to what might one might call the Genet Principle: that the underdog is always right. From now on, like Jean Genet, Sartre submits himself joyfully to the alienated, downtrodden, thwarted and excluded. He tries to adopt the gaze of the outsider, turned against the privileged caste — even when that caste includes himself.
No one could say that this is easy to do, and not only because (as Beauvoir had pointed out in The Second Sex) borrowing someone else's perspective puts a strain on the psyche. Anyone who tries to do it also runs into a mass of logical and conceptual problems. Disagreements inevitably ensue about who exactly is least favored at any moment. Each time an underdog becomes an overdog, everything has to be recalculated. Constant monitoring of roles is required — and who is to do the monitoring?
I'm surprised I've never heard this idea cited approvingly and credited to him. Sartre, the unheralded father of intersectionality? Well, that would certainly explain why the baby is so fucking ugly.