When Petrocelli, the prosecutor, refers to "monsters in our communities," she is emphasizing the idea that there are individuals who commit heinous acts, such as stealing and killing, which fundamentally disregard the rights and dignity of others. In this context, "monsters" symbolizes the extreme moral failure of criminals who engage in violent or harmful behavior.
Her statement implies that while we often think of monsters as fictional or metaphorical, they manifest in real life through the actions of those who choose to commit crimes. This does not mean that she believes these individuals are literally not human; rather, she is highlighting the severity of their actions and the moral consequences of their choices.
So, the most fitting interpretation of her statement would be that criminals do not respect humanity, as they act in ways that harm others and violate social norms and laws.