What is the overall tone of kings argument? What words and phrases indicate this tone?

“My Dear Fellow Clergymen:”

Dr. King’s tone as he begins his letter is remarkably restrained. Considering the context – he was in solitary confinement when he learned that Birmingham clergymen had together issued a statement criticizing him and praising the city’s bigoted police force – he had every reason to make his letter a rant. And yet this address announces his purpose loud and clear: he aims not to attack but to explain. Rather than indicate what separates him from the other clergy, he calls them “fellow clergymen,” underlining one of the letter’s main themes: brotherhood. Of course, there is no shortage of passive aggressive attacks and criticism throughout the letter, but the tone remains polite, deferential, at times almost apologetic, creating a friendly and ironic tone. This marvelous collection of attributes is present from these very first words.