According to the text, why does Douglass say that "learning to read has already come, to torment him?"

Learning to read made Douglass understand just how horrible and futile his situation was. What became clear to Douglass was that his master was right – learning did make slaves intractable and unmanageable. He came to perceive slaveholders as no more than "a band of successful robbers" who had gone to Africa and stolen them from their homes. He felt discontentment surge through him and often wondered if learning to read had been more of a curse than a blessing. His enslavement tormented him unceasingly.