The defense mechanism where an individual justifies their behavior with socially acceptable reasons is:

Rationalization is a psychological defense mechanism where an individual provides logical or reasonable explanations for behaviors or actions that may otherwise be viewed as inappropriate or socially unacceptable. By offering socially acceptable reasons for their conduct, the person alleviates feelings of guilt, shame, or anxiety that may arise from the behavior. This allows them to maintain a positive self-image and avoid confronting the true motivations or emotions behind their actions.

For example, if someone engages in excessive spending, they might rationalize it by saying they are investing in their happiness rather than addressing the underlying issue of financial irresponsibility. This mechanism serves to protect the individual's self-esteem and can make it easier for them to navigate social situations without facing the emotional distress associated with their true behaviors.