What reason does King give for writing this letter?

King wrote this letter in response to criticism by the clergy for his presence and work in Birmingham. He says that because he believes their criticisms sincere and without malice, he wished to answer their charges.

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. If I sought to answer all the criticisms that cross my desk, my secretaries would have little time for anything other than such correspondence in the course of the day, and I would have no time for constructive work. But since I feel that you are men of genuine good will and that your criticisms are sincerely set forth, I want to try to answer your statement in what I hope will be patient and reasonable terms.