Does the rest of the paragraph help us find the answer to the question (mentioned at the beginning of the paragraph)?

Referring to.....

While confined here in the Birmingham city jail, I came across your recent statement calling my present activities “unwise and untimely.” Seldom do I pause to answer criticism of my work and ideas.

King knows why he paused because he is trying to articulate that white clergy has done little to help the Black Civil Rights movement.