I have been assigned to write an essay about Kathy Knapp's analysis of T. C. Boyle's The Tortilla Curtain. She says the novel "captures the ethos of the gated community." I need help understanding how Knapp defines that ethos.

Kathy Knapp writes in "Ain't No Friend of Mine" (see the source below) that the gated community in The Tortilla Curtain "embodies in miniature the nation's schizophrenic relationship with its undocumented community" (page 122). Knapp states that homeowner associations, such as the gated community where Delaney and Kyra Mossbacher live in the novel The Tortilla Curtain, generally allow undocumented immigrants into the community to perform chores such as housework and gardening. In other words, the white community only recognizes undocumented workers when they want work done, such as having their children cared for or having their pool cleaned.
In the novel The Tortilla Curtain, Cándido Rincón and his wife, América, undocumented immigrants from Mexico struggling to survive around Los Angeles, are invisible to the wealthy suburbanites in the Arroyo Blanco gated community. When Delaney Mossbacher, a resident of Arroyo Blanco, hits Cándido with his car, Delaney gives Cándido $20, later stating that it's sufficient compensation because the man is Mexican. In other words, Cándido's life is of little value to Delaney. However, residents of the Arroyo Blanco gated community employ América as a cleaning lady and pay her very little in return for her work, and they employ other undocumented immigrants as gardeners. The characters in the novel practice the ethos that Knapp discusses as they only value and see undocumented immigrants when the immigrants can be helpful to them as very low-paid workers. Otherwise, the characters do not recognize or try to help undocumented immigrants such as Cándido Rincón and his pregnant wife, América.
Source:
Knapp, Kathy. “‘Ain’t No Friend Of Mine’: Immigration Policy The Gated Community, And The Problem With The Disposable Worker In T. C. Boyle’s Tortilla Curtain.” Atenea 28.2 (2008): 121-34. Print.