I haven't seen Pangs, but Wikipedia gives us a synopsis. Here are the Native aspects of the story:
A green haze comes up from the old Mission and goes to the Cultural Center where some weapons are being kept. After the haze comes in contact with a spear, it turns into a large Native American man and kills the curator. Buffy and Willow later secretly investigate the murder, and wonder why the curator's body was missing an ear. They discover that a Chumash spear is missing. Buffy tells Giles about the murder while planning to have Thanksgiving at his place.
Buffy goes to find Father Gabriel, a priest who may have information for them, but finds that a returning Chumash spirit has killed him. After the mission was uncovered, his spirit was released to reenact the wrongs that were done to his people. Buffy and Giles talk about it while working on dinner. Then Willow shows up with a stack of books on the Chumash. She explains that while they were once peaceful, the people of Sunnydale horribly mistreated them. Cutting off a victim's ear is how they proved that a kill was successful. Willow and Giles argue about what happened between the Native Americans and the people who took their land and their lives.
Everyone begins to argue about what they're going to do to stop the spirit. Willow doesn't want to kill him, but everyone else argues that that's the only way. While Willow, Anya, and a weakened Xander go to find the Dean and warn him his life may be in danger, the spirit calls forth more spirits to help him get revenge for their people.
The spirits attack Buffy, Giles, and Spike with arrows. Helplessly tied to a chair, all Spike can do is try to move out of the way as he gets hit with arrows. Willow, Xander, and Anya encounter Angel on their way back and they determine that the Chumash went after Buffy. Buffy tries to go for more weapons, but gets an arrow in the arm. After riding over on bicycles, the Scooby Gang tries to attack the Chumash spirits as best they can with shovels. Angel shows up and helps them out. Buffy cuts one of the Chumash with his own knife, and reaches the conclusion that their own weapons can kill them. The spirit turns into a large black bear, which Spike desperately tries to get away from and ends up knocking the chair over. Buffy struggles with the bear and then stabs it. All of the spirits disappear.
Angel walks away without being seen by Buffy, and later, the gang sits down to Thanksgiving dinner.
Willow (from Buffy) on Columbus Day and Thanksgiving
And here are my thoughts on it:
Moreover, the Spaniards' actions are only historical words while the spirit's actions are present-day dangers. The Indian is the only one cutting ears now. This makes him seem more brutal and savage.
After killing anybody, even a spirit, you might think about canceling your celebratory dinner and instead reflecting soberly on your actions. But no...Buffy and company sit down and eat as if nothing's happened. As if the genocide of Indians is ancient history of no consequence to anyone.
Suppose one of Buffy's friends had been a Chumash Indian. Imagine how the dialogue would've gone then: "Sorry about exterminating your ancestors--again--but we didn't have a choice. Our ancestors had to kill your ancestors and so did we.
"Anyway, it's over now, so forget about it. Would you prefer dark meat or white meat with your potatoes? Bon appétit!"
Dialogue proves Buffy's bias
If you think Buffy wasn't sending a message about Indians, think again. Here are some key snippets of dialogue from the characters' "argument" about Indians:
Spike: You won. All right? You came in and you killed them and you took their land. That's what conquering nations do. It's what Caesar did, and he's not goin' around saying, "I came, I conquered, I felt really bad about it." The history of the world is not people making friends. You had better weapons, and you massacred them. End of story.
Spike: You exterminated his race. What could you possibly say that would make him feel better? It's kill or be killed here. Take your bloody pick.
Xander: Maybe it's the syphilis talking, but, some of that made sense.
What could Buffy and company possibly say to make the Chumash spirit feel better? How about, "We'll tear down the mission and raise a Chumash monument in its place"? How about, "We'll sue the Catholic church for reparations for the lost land and lives"? How about, "We'll force the US government to uphold its Chumash-related treaties and recognize Chumash sovereignty"? Any of these responses might've been enough to placate the angry spirit.
For more on the subject, see Chumash = "Fluffy Indigenous Kittens"? and TV Shows Featuring Indians.
Below: Spike the Indian hater gets pin-cushioned with Chumash arrows. Unfortunately, he's already dead so they don't harm him.