I think Munch hated the scream as much or more than anybody else, but felt compelled to paint it because that was the only way he could relate to the culture he lived in. He was surrounded by it, and the only way he could respond to it was to paint it in his awful expressionistic style. He took a vacation to an Island where he painted "The Sun," a happy painting, perhaps the only happy painting of his life.
It's like German expressionist painting. They're all angst-ridden and awful, painful depictions of the culture. Expressionistic music is the same way. Berg's operas Lulu and Wozzeck are atonal works full of nothing but depravity, pain, murder, rape, and violence.