While Luther was away, Andreas Bodenstein von Karlstadt (famous for changes in the church) and Thomas Muntzer took it upon themselves to be the new leaders of the reformation.
Karlstadt was a lot like Luther; he shared some of the same ideas, and was also a professor at Whittenburg. Muntzer learned a lot from Luther and at first looked up to him as well. However, these kind things didn't last very long.
Luther criticized both these men because of the new ways they where teaching. In Luther's letter "Opposition of the Fanatic Spirit" he states, "These prophets have little sympathy, taste, or understanding"; "They...want people to be amazed at their great skill". It seems that he feels Karlstadt is only in it for the glory of himself and because of it "Christ is forgotten".
Luther is not any more pleasant in his critiquing of Muntzer. In his letter to the "Princes of Saxony concerning the rebellious Spirit", he mentions that Muntzer wants to, "enforce faith in an immediate and dictatorial manner". It's obvious Luther doesn't agree with this tactic.
I think that it's easy to say that both Karlstadt and Muntzer would want to respond to the criticism and have people listen; however, being the popular man Luther already was made it tough for them to get through to the more important people. For example, Luther's letters stated above probably had more people follow his word then Muntzer's rebuttal in his letter to Frederick the Wise. Muntzer was furious with Luther's letter calling Luther a, "mendacious man" and states that Luther is a, "pompous tyrant, and full of ferocity and hate."
All three of these men no doubt have already had a great impact in the reformation. It seems