Answer: Atticus is explaining Scout that, although you can be "influenced" to have a certain opinion about such a controversial topic, no one can actually tell you what to think.
Explanation:
During the trial, people in town assumed that Tom Robinson was guilty, and the main reason to believe it was that he was a coloured man, but still Atticus defends his opinion explaining Scout that, even though it would be easier to assume Tom's guilt, he will defend his innocence because it is what he believes in his heart.
