Your paper is about the people in your sources, not the sources themselves. When working closely with the writings of a historical subject, it is easy to forget to identify the author of a thought. Often, YOU wind up looking like the author. This looks like your thought when it is really Garrison's. The implication here is that black parents think the book should be banned, but the sentence technically reads that the author of the paper thinks this.
History takes place in the past.
Use the past tense and avoid the present tense. Keep tenses consistent. A great scholar once told me that good writing is in the verbs. Make sure you define important concepts. If you argue that Jefferson was neurotic, make sure you define that term.