Eddie's relationship with Mr. Stiles is rather tragic. It starts off somewhat positively, though Mr. Stiles could be interpreted as exploiting the fact that Eddie is willing to work for much less money than Mr. Stiles would have to pay someone else. Eddie likes Mr. Stiles, though, and Mr. Stiles seems to like Eddie. Eddie says that he is "a good person": "Now and then he brought me glasses of iced tea or a soda. He fixed me and himself a sandwich, with a red plastic basket of potato chips."
One might believe that Eddie screws up by not reporting the theft of Mr. Stiles's truck, but I wonder if that would have resulted in terrible consequences for Eddie from the gang members in his neighborhood. It seems as though Mr. Stiles does not want to rush to judgment about Eddie's character, but he does not know what to think when Eddie disappears with his truck and never returns. Eddie feels bad because Mr. Stiles "was a good guy, and [he] wanted him to know that [he] didn't mean him harm." When he learns, later, that someone driving his truck did some violent crime at a laundromat, Mr. Stiles thinks it is at least possible that Eddie could have had something to do with it, and he sets Eddie up to be arrested.
Ultimately, Mr. Stiles seems to forgive Eddie because he understands that Eddie didn't steal his truck and didn't know how to handle it. Eddie forgives Mr. Stiles because he understands how things must have looked to Mr. Stiles, and Mr. Stiles genuinely does seem to be a person with good intentions who tries to fight the prejudices that society has inculcated in him. Given that both men have such good intentions and are just trying to do the right thing, I feel I would have been forgiving in either position as well.