As the sub heads through robot-controlled waters to pick up a package, crewman Dietz objects to taking orders from "metal":
Hauling ass through the worst of Indian country? And for what? To take a damn box back to Serrano?
But the crew members are mainly Euro-American soldiers. And the term accurately reflects a US military mentality. By showing that some soldiers think stereotypically, at least it's honest.
True, it would be better if someone had contradicted this politically incorrect usage. Leaving the notion that Indians = robots unchallenged isn't nice. But at least Terminator's writers are still thinking of Indians.
Previous Native references in the show:
Coyote in Terminator
Native souls in Terminator
Cabeza de Vaca in Terminator
Modoc War in Terminator
For more on the subject, see TV Shows Featuring Indians.