Answer:
The men have come to hurt Tom who had been accused of ra ping a white girl.
Atticus was there to guard Tom from any harm.
The men's ideas of justice is different from Atticus in that he believes in the fair justice system while the men did not. They would rather judge a person based on his appearance and skin color.
Explanation:
Harper Lee's "To Kill A Mockingbird" revolves around the theme of racial discrimination in Maycomb. Though narrated from the youngest character's perspective, the novel still managed to show the reality of the American south and what life is like.
Chapter 15 shows the scene where Tom Robinson had been kept in jail.Tom had been accused of ra p ing a white girl, due to which he has been put on trial. Now, Atticus knows that some people who want Tom to be convicted will try to do something bad before the trial so he went to stay on guard at the jail. A group of men did turn up to see Tom but Atticus stood his ground and did not let them pass. They had come to ly nch Tom and kill him, rather than make him stand fair trial for the alleged ra pe.
Atticus knew some trouble may turn up so he stood guard with Mr. Underwood, guarding Tom and makings sure he is safe from the wrath of the white folks.
The group of men thinks that justice cannot be given to someone like Tom for a ra pe case, considering that he is also black. To them, black men are not capable of telling the truth and that they deserve to be punished. Atticus, on the other hand, believes in a fair trial and would do anything to prove Tom's innocence as long as it takes. He is a good lawyer who believes in the justice system and the system of "innocent until proven guilty".