Major Barbara is structured by a contest between father and daughter for the other's soul and the path of salvation. Each agrees to visit the other's workplace and allow the other to attempt their conversion. Undershaft's visit to the Salvation Army shelter takes place in Act II; Barbara goes to the armory with her family in Act III.
As discussed in the preface, Shaw's portrait of the shelter is fundamentally a critique of the Salvation Army's flaws. One of the many criticisms Shaw underlines, for example, is that the Army forces its clientele to pander to the saintliness of its workers. In this sense does the work of the Army have less to do with the condition of the poor than the narcissism of its officers. More importantly, the Army fails to realize that man does not need redemption from sinfulness but from the material abjection of poverty, hunger, and sickness.
Unlike the shelter, Perivalee Saint Andrews appears as a paradise of social engineering. Undershaft has redeemed his men more successfully than preaching ever could by eliminating poverty. He does not do so for the love of the masses. Certainly Undershaft provides for their comfort to assure his company's productivity. He also, however, considers poverty the worst of man's crimes. For Undershaft, the "crime of poverty" is a crime committed against society by the poor themselves. The poor, appearing as abject masses from some paranoid fantasy, "kill" society's happiness, forcing the ruling class to eliminate its liberties and organize "unnatural cruelties" to keep them in check.
Thus Undershaft will pit himself against poverty in the name of order and cleanliness. Indeed, for Undershaft, order and cleanliness are categorical imperatives of sorts—they justify themselves. Though the realization of these imperatives would ostensibly benefit the masses, we can readily imagine how they might come at their expense as well. Simply put, the institution of order and cleanliness easily means the elimination of the disorderly and unclean. Note in this respect Undershaft's chilling invocation of the Salvation Army's motto in Act I: "My sort of blood cleanses: my sort of fire purifies."