Argument about A Yellow Raft in Blue Water and racism

My thesis already done- In his 1987 novel A Yellow Raft in Blue Water, Michael Dorris uses his three main characters to argue that people of color(specifically Native Americans in this book) are mistreated and have many forms of racism shown against them, through character analysis during each time period it is shown that there has been no change in racial issues throughout the whole time period shown in the book. Michael Dorris was a first chair on Native American Studies at Dartmouth and believes that there should be more change done in the world to end racism and start treating people with equal respect no matter their skin color. 

I need you to argue for why the author is bringing it up and how he uses the characters to imply that.

I need at least one quotation from the book itself, https://pac.lfpl.org:2068/stable/pdf/43019429.pdf?ab_segments=0%2Fbasic_search_gsv2%2Ftest&refreqid=fastly-default%3Afeb3b07eb4ce6c5e6ce2c2b7b91cdcd2, https://pac.lfpl.org:2068/stable/pdf/20736895.pdf?ab_segments=0%2Fbasic_search_gsv2%2Ftest&refreqid=fastly-default%3Afeb3b07eb4ce6c5e6ce2c2b7b91cdcd2, https://pac.lfpl.org:2068/stable/pdf/20739323.pdf?ab_segments=0%2Fbasic_search_gsv2%2Ftest&refreqid=fastly-default%3Afeb3b07eb4ce6c5e6ce2c2b7b91cdcd2, https://pac.lfpl.org:2068/stable/pdf/20736505.pdf?ab_segments=0%2Fbasic_search_gsv2%2Ftest&refreqid=fastly-default%3Afeb3b07eb4ce6c5e6ce2c2b7b91cdcd2,  and https://pac.lfpl.org:2068/stable/pdf/3814612.pdf?ab_segments=0%2Fbasic_search_gsv2%2Ftest&refreqid=fastly-default%3Afeb3b07eb4ce6c5e6ce2c2b7b91cdcd2