This novel explains how Gabe became a career criminal. The reason it does that is nested in the story, because Gabe meets a racist who makes all kinds of offensive, bigoted claims about those "foreigners," like Gabe and his family. This is the most explicit depiction of the main theme of the novel: Gabe's unlikely demise into a corrupted life.
But that doesn't mean that Gabe is a villain necessarily. Rather, the novel explores an alternative narrative. Basically, the question raised by the novel is about assumptions. Why do we assume that criminals are evil, instead of assuming that horrible things might have happened to them? This is echoed in Gabe's confrontation with the tow truck driver who claims that immigrants don't learn English because they're stupid and lazy. This hateful narrative is very similar to the hateful narrative about crime in disenfranchised communities. In Tomas's case, yes, crime was the overflow of his anger and willingness to harm others. But, for Gabe, many many obstacles had to obstruct him before he was caused to fail.
In other words, the difference between Gabe and Tomas is that Tomas immediately used his hatred toward his father as an excuse to be evil. Gabe never wanted to be evil, but his circumstances continually limited him until finally, he was forced into crime. Afterward, perhaps he is ultimately responsible, but to say, "Immigrants are naturally criminals" would be incorrect. This novel is a response to closed-mindedness.
