TR's so set on discussing the climactic struggle between good and evil in "The Man with the Muckrake" that he may as well turn in his presidency and become a knight errant.
He firmly believes in absolutes and in every person's power to choose between good and evil. To him, there's no acceptable sin and no just target. We'd imagine he wouldn't be a big fan of Robin Hood, either. He doesn't believe that any one group can be all good and all evil, like rich people in this speech's instance, but each person has to make that choice for him or herself.
Theodore Roosevelt, in his worldview of "everyone has moral choices," seems to ignore very real problems that move people to make certain decisions in this speech; however, in his presidency he was able to make some major changes to the system. This speech seems like his advice to the public, while his work in office attempted to cut down situations that might push people toward crime.
This mindset of good vs. evil casts Roosevelt, naturally, on the side of right and righteousness. His foreign policy, that of American expansionism through naval power, used that righteousness to justify military force.
In Teddy's own words, "The liar is no whit better than the thief" (17).
The main damage that TR seems to be concerned about in "The Man with the Muckrake" is slander. It's also a speech mostly targeting journalists, and there's pretty much only one kind of weapon in their "wrong-doing" arsenal.
Just like a certain boy who cried out about a certain lupine animal, Teddy Roosevelt's afraid that, if there's a general atmosphere of lies and slander, then nobody will believe the truth—or even believe in truth at all. Given his outlook on life, particularly in the absolute truth department, he has a vested interest in making sure this doesn't happen.
Roosevelt's fears of deceit in the newspaper stemmed heavily from the fact that, during that time period, there was a vast multitude of newspapers in the pockets of whomever could afford to own one. Not only that, but if you owned a newspaper, you got to dictate the content. Beyond a scout's honor promise of journalistic integrity, there was nothing compelling newspapers to publish the unvarnished truth and even less compelling them not to exaggerate headlines to make a buck—headlines that today might look like, "16 Reasons Why Carnegie Steel Put Down the Homestead Strike, and Number 5 Will Surprise You!"
One of the reasons Teddy Roosevelt hates deceit so much is because of how much he values the individual American character. His politics are all about trying to make the system fair for everybody and asking people in return to be stand-up human beings.
Class warfare is the problem behind all of this hemming and hawing about morality, honesty, and virtue. The wealth gap was one of the defining issues of the Gilded Age, and corruption in politics and business was on everyone's minds, along with the escalating conflict between factory workers and their employers.
While TR is super aware of the class conflict, by addressing it in "The Man with the Muckrake" he wants to replace the conflict with an alliance of good workers and businesses against bad workers and businesses, obliterating class lines.
In this speech, Roosevelt seems to ignore all of the extra powers corporations get from their oodles and oodles of money. While it's true that rich men and poor men alike can be good or evil, the rich evil man has a lot more power to throw around.
With the working class, Teddy's most freaked out about violent uprisings. The assassination of William McKinley might have been an influence in this line of thinking, or the Haymarket bombing in Chicago. Roosevelt lays out the tools for evil that each class uses: for the rich, it's their money and influence, and for the poor it's their influence to get desperate people to go out and do violence.