"…boats against the current…"
The individual, in this case the criminal, rarely, if ever, acts from a "point from nowhere." Even what seems to be a sadistic, amoral, wholly selfish act is, in fact, something that is highly moral, communal, and, even in cases of violence, possibly benevolent. But the individual's actions are not only presently informed by social and moral factors, they are pressed upon by those various historical facts that led up to this moment that is the individual's action. Just as the individual action never occurs in a vacuum, so too is an "individual" impossible without cultivation, a history, a past. The possible horizon of actions, the sets of values, the notions of what constitute dignity, success, and recognition are always already pressed upon by the social, economic, political, and historical antecedents that have led up to the moment of will, decision, and action, the "moment" of individuality.
It would be erroneous to simply reduce the individual to a mere token of class, race, or gender, but it is just as grave an error to pretend that the histories that have led to the construction and development of these aspects of an individual are irrelevant. We cannot think of individual organism apart from the environment in which their habits and values were formed. Organisms shape their environment to ensure survival. But the environment also shapes the organisms that inhabit it. An organism cannot simply "decide" to get up and leave the habitat and history inside which it grew and lives. To do so would require a whole new set of adaptations and habits, something that is extremely difficult, if not impossible, and may ultimately lead to the organism's death. This is not only the case for biological environments, but for moral environments as well. We see this explicitly with several characters—D'Angelo, Wallace, even McNulty—who try to "change" through a heroic act of will without a corresponding change in environment. In the case of D' and Wallace, we see the bloody death that awaited them both.