It's helpful to remember that Dr. King was a Christian minister, meaning that his approach to activism was partially informed by his religious worldview. In particular, this worldview promoted the value of love, fellowship, and peace. Instead of challenging racism through violence and anger, then, he drew upon his faith in humankind’s ability to show love and compassion for one another. Nonviolent direct action was therefore a perfect way to challenge injustice without actually doing anything immoral, which is why Dr. King believes that it’s an honorable method that “ennobles” the people who use it. By peacefully and levelheadedly refusing to cooperate with an unjust system (which is what Rosa Parks did in Montgomery, Alabama, when she declined to give up her seat on a segregated bus), activists were able to stand up to their oppressors while maintaining a sense of morality.