Notice how in the first two sentences, the “slavery wasn’t that bad” sentences, the main subject of each clause is a person: slaves, masters, slaveholders. What those people, especially the slave owners, are doing is clear: They are treating their slaves kindly; they are providing adequate food and clothing. But after those two sentences there is a change, not just in the writers’ outlook on slavery but also in their sentence construction. There are no people in the last two sentences, only nouns. Yes, there is severe treatment, whippings, brandings and torture. And yes, those are all bad things. But where are the slave owners who were actually doing the whipping and branding and torturing? And where are the slaves who were whipped, branded and tortured? They are nowhere to be found in the sentence.
Grammar and voice are REAL.