The Street Lawyer is actually not the main character of the novel—he's the "insane shooter" from the intro sequence, which sets up the dilemmas of the novel quite nicely. It turns out, the homeless man who takes the powerful, wealthy lawyers hostage at gunpoint was actually wrongfully evicted by this firm, and furthermore, the firm knew that it was illegal and they did it anyway because this homeless man was powerless.
The novel's focus on power versus powerlessness continues, because Brock has to analyze what the homeless man said. As he explores the reality of the situation, he puts this much together: to aim a gun at someone was completely uncalled for, but actually, if the person had refrained from violence, perhaps he could have legitimately sought justice for this.
That points to the real dilemma. The homeless man with the gun isn't crazy. He just doesn't understand the American legal system, because it's very complicated, and because the lawyers pay a lot of money to figure it out. And, there's this kicker to consider: law itself is predicated on assumptions, and as Brock explains in the denouement, American law is conflict-oriented. Thus, the powerful always win because they have more powerful resources to use in combatting the weak.
