Process of writing argumentative letters

While writing my collection of argumentative letters I have been struggling with a few aspects. It is challenging for me to make it an argument. I have been having trouble making disputing with MLK rather than just agreeing with him. I am having the most trouble with the organization of the letters. I have it so that there is 9 different letters being sent. I think that will be too much and I need to shorten it. I also have written it so I write a letter on a topic then he responds and so on. I want to change my essay so that I write a letter on several topics and he responds to all my points, thus shortening the amount of letters.