There’s a scene in which Ethan and Martin are taken to three white woman who have been in Indian captivity in the hopes of finding Debbie, she is not with them but we see that the women have been driven mad by their time with the Comanche.
This scene is important as it foreshadows their eventual meeting with Debbie. They have not seen her since she was captured and this is their first encounter with people who have been through what she has, and this encounter therefore shows them how she may be when she is found.
Ethan’s believes that the women "ain’t white. Not any more. They’re Comanch” he views Debbie in the same way; no longer white and therefore not worth saving . Ethan's reaction upon seeing the women, and lack of sympathy for them shows his contempt towards Native Americans and is similar to his attitude towards Martin, because both Martin and these women have come into contact with native Americans; or have native American ancestry in Martin’s case, they have been contaminated in his eyes.
The scene also shows the films conflicting portrayal of native Americans. We are not meant to necessarily sympathize with Ethan's view but, the scene does not contradict it, the women have been negatively effected by the Native Americans seemingly reinforcing Ethan’s ideas of Native Americans.