Why does John hate Popé so much?
John disapproves of his mother's status as the tribal whore, and he cannot understand her when she tries to explain that that is the way things are done where she comes from in "the Other Place" because that's not what he knows, having been born and reared on the reservation. He looks at Pope as an intruder into his world with his mother, too. And Pope also brings Linda mescal (think mescaline, from the peyote cactus), which Linda takes in excess in an attempt to get that soma holiday back, and John despises seeing her that way.
Ironically, due to Linda's attachment to Pope, he's almost like a father figure to John, and with John's disapproval of their relationship, it makes for a pretty dysfunctional family!