He goes back to make things turn out better. It includes homophobic and racial slurs and other deeper points as the movie tries to make the case that the butterfly effect, chaos theory, play huge roles in determining the kind of people individuals turn out to be based upon events & decisions large and small they experience. Or stated another way, that people are products of their environments.
But my take is that people are products of their environment only to the extent they allow their environment to shape their development. Because obviously people react differently even when they are subjected to similar environments. So people turn out the way they are because of the individual and how they personally react to their environment. How they chose to react is what shapes them.
He blacked out in the basement. Thus he “relived” that experience at least once.
Sick.