He had been very interested in the notion of emancipation and had studied over it a lot while he went about his work. It was obviously just pure luck that he himself hadn't been born a slave, but if he had been unlucky Lincoln would have freed him. (1.91)
Because Lonesome Dove never explicitly tells us what in year the action takes place, Deets's ideas about abolition help us place the book somewhere in time. Deets is old enough to have been born a slave. The 13th Amendment was ratified 1865, so we know the book takes place a decade or two past that.
"I'm as American as the next," [Call] said, taking his hat and picking up his rifle.
"You was born in Scotland," Augustus reminded him. (1.95-1.96)
Race isn't just about skin color. Gus makes a good point here: many Americans at this point in history were still immigrants, from one place or another. For the most part, the only really native Americans were, um, Native Americans.
[Call] looked at Deets when he said that. He could not formally make Deets the leader over two white men, but he wanted him to know that he had the responsibility of seeing that the horses got there." (11.68)
Despite what we said about abolition, there is still racial tension in the country between white men and black men. White men don't want to take orders from black men. Have things changed?
"If I'd wanted a yellow husband I'd have married a Chinaman."
"What's a Chinaman?" Joe asked.
"Go get a bucket of water," Elmira said. (27.23-27.25)
This bit of apparently casual racism shows just how rural some people were back then. Elmira knows what a "Chinaman" is because she used to live in a bigger city, but her son has never left Fort Smith, Arkansas. He probably couldn't even find China on a map.
The fall convinced him he had lived long enough with Americans. They were not his compañeros. Most of his compañeros were dead, but his country wasn't dead, and in his village there were a few men who liked to talk about the old days when they had spent all their time stealing Texas cattle. (41.35)
Bolivar is conflicted because he has lived for many years as a Mexican man with white cowboys—white cowboys who steal from Mexicans. He's caught between worlds and has no idea what to do.
Frog Lip didn't say much. He was a black man, but Jake didn't see anyone giving him many orders. (68.3)
This quote recalls Call's thought about not being able to make Deets a leader because Deets is black. Here, the theme is expanded upon. Jake Spoon expects to see Frog Lip (a racist name in and of itself) given orders simply because he's black, even though he's the most skilled man of the group.
"You coming?" [Frog Lips] asked—the first time on the whole trip that he had spoken to Jake directly. There was an insolence in his voice that caused Jake to flare up for a moment despite himself. (71.19)
You can substitute "insolence" for "uppitiness" here: Jake only interprets Frog Lips's tone in this way because Frog Lips is black. Jake doesn't feel this way when other people give him orders.
"Oh, you've got a n***** for a scout," Dixon said. "No wonder you're lost."
"We ain't lost," Call said, annoyed suddenly, "and that black man could track you across the coals of hell." (83.77-83.78)
Not everyone is totally racist here. Call stands up for Deets and his fellows know that Deets is a better tracker than anyone in their group, regardless of skin color.
"Leave me that n*****," Weaver said. "I've heard they can smell Indians. They're just red n*****s, anyway." (83.124)
In contrast to Call treating Deets as a human, Weaver treats Deets like he's a horse he's trying to requisition. That's about the nicest thing we can say about Weaver here, frankly.
The fact that the Indians were laughing and seemed friendly made it difficult. How could you shoot people who were laughing? (67.118)
Some men would shoot any "Indian" simply because they're Indian. Newt was raised in that type of world, so this little scene is a learning experience for him. Indians are people, too, he realizes.