Roosevelt means that a muck-raker - a journalist- is that person interested in dirt or filthy things - muck-. That person will do anything to get filthy information and to get it, he / she will use a rake to scratch the soil - or reality - to pick up or invent the dark side of humans. Roosevelt is furious because a group of journalists have disclosed controversial issues from his government. He shows his anger through this speech on "The Man with the Muck- Rake" (1906).