The Boondock Saints movie exhibits and demonstrates many possible causes and reasons for social deviance. One example of this is shown in the Subjective view of deviance through a Constructionist Theory. The Subjectivist believes that a deviant person is a conscious, feeling, thinking subject and that one should understand the experience of that person. From a Constructionist perspective, deviants are actively seeking meanings in the deviant activities.

The brothers in the movie are seeking meaning from their killing. They believe that they are on a mission from God, and that they will be protected and blessed for doing this.
The brothers in the movie are a good study on mass murder. While they are not murdering everyone at exactly the same time in the same place, they are doing it in a cult-like sort of way. They believe that they are on a mission from God, to kill all criminals in Boston.

They believe that they are following a direct order from God, much like what certain cults believe. Most of their murders are also pre-meditated.Perhaps the biggest factor in why these brothers murder can be attributed to the theory of Subculture of Violence. Subculture of violence states that those who are poor or less fortunate are more likely to engage in violent acts, such as murder and rape.

This is attributed to their social standing, and their inability to get out of the lower social classes. The actual cause of violence in these situations is poverty and social inequality. While the brothers are not lashing out at those who are significantly richer than them, they are lashing out at those who are more powerful than them. They are also lashing out at those who make others poor and impoverished.Last but not least, one can also look at the brothers' acts as acts of terrorism. These murders are not terrorism towards the general populace, but towards those who are criminals, and to those who might become criminals.

Terrorism is defined as violence directed towards a government, with the intent of forcing the government to do a specific act. The government in this situation is a mafia family, and all those who form a criminal government within the city. The acts that the brothers are committing are intended to send a message of "stop what you are doing now" to those who are committing murder, rape, extortion, and other criminal acts.