Why would Fiona, a trainee in the care of the old, probably accept the pratice of releasing the old?

She would probably accept this practice because she would be trained to believe it was normal.  Also, people in this community are devoid of emotions, so there is no reason that she would consider the practice cruel or merciless.  While Fiona is painted as a sweet, caring, and kind girl, this only adds to the sad fact that even the most congenial of characters can become doers of evil in a society that controls their citizens' every move.

Lowry shows throughout this book that each character is capable of falling into evil.  Perhaps the most important of these illustrations is that of Jonas' father "releasing" or murdering an infant because it was born weighing less than his twin brother.  All characters are capable of doing horrible acts, all in the name of doing their jobs in the community.