Why did all the blacks on the balcony stood up as a sign of respect for Atticus?

When Atticus passed, the black people wanted to show respect for Atticus because they wanted to thank him for trying to save Tom Robinson. Even though Tom was charged as guilty, Atticus did his best to try and save him. No one agreed with Atticus, and at one part, some townspeople even tried to kill him, but he never gave up.