When the Viet Cong seemed to be winning the war in South Vietnam in 1961, how did President Kennedy react?

In this excerpt, the word tension means discomfort. Dr. King is saying that a certain level of discomfort is necessary for growth as a country. The group(s) that have been oppressing the black community are to expect nothing short of discomfort. Facing difficult emotions is the only way that we, as a community, can make any sort of change.