What rationalization does Boy make about his relationship with “the free‐ spirited girls he met in Toronto” ?

Boy does not consider cheating on "free spirited girls of Toronto" to be of any consequence. He did however take cheating on Leola more seriously.

Boy, however, had acquired tastes in the Army that could not be satisfied by agonizingly prolonged and inadequately requited puffings and snortings in a parked car, but he had no clarity of mind that would ease him of guilt when he deceived Leola—as he did, with variety and regularity among the free-spirited girls he met in Toronto. He built up a gimcrack metaphysical structure to help him out of his difficulty and appealed to me to set the seal of university wisdom on it.