B)He is comparing muck-rackers to people who focus on negative things.
Explanation:
In this speech, Roosevelt talks about journalists, and he compares them to "muck-rackers." He tells us that muck-rackers are people who can only focus on the filth that they find on the floor, and never look towards spiritual things. Roosevelt implies that journalists are similar, as they only "fix their eyes on that which is vile," or in other words, are only able to focus on negative things.