The Batman has strong messages about class divide, with the main driving force for The Riddler being the injustice within Gotham City. Despite Bruce Wayne's tragic upbringing, it's pointed out that he had it much easier than other orphans in the city. While this doesn't give Riddler the right to target Bruce, he does have a point that the billionaire can't fully understand their struggles. And this is only made clearer with The Riddler's choice of murder weapon.
The opening sees The Riddler bludgeoning the Mayor-elect with a carpet tucker, a simple tool used to neaten up the edges of carpets. As with everything The Riddler does, the weapon provides a hint to his overall goal, as his ultimate plan is hidden underneath the carpet in his apartment. Which, unfortunately, isn't discovered by Batman until it's too late.
After The Riddler lets himself get captured, his home is found in a grungy apartment complex. The police and Batman all search high and low for any clues, but only a locked computer and envelope are found. Up until this point, Batman has been on top of every riddle, often solving them the moment they're found. But he fails to piece together the carpet tucker, until he gives the apartment a second look later that night.
With a failed interrogation of The Riddler, Batman sneaks his way back into the crime scene. The only other person there is a cop, who begrudgingly lets him look around. Batman once again examines the murder weapon, confused as to what it is. The cop casually reveals it to be a tucker, which he's seen due to his father working with carpets. It's here that Bruce puts two and two together, and removes the carpet to find the Riddler's entire plan.
Batman would've completely missed this clue if it wasn't for the son of a blue-collar worker, as his life of privilege kept him away from such work, even something as simple as house decoration. And Bruce pays the price for his ignorance, as they discover the computer password and the plan to flood Gotham City -- with no time to stop it.
And it's not the first time Bruce is faced with the class divide, as he uncovers all the corruption within the Gotham City Police Department. And even during the mayor's funeral, a stranger talks to Bruce about why he deserved to die, mentioning that the mayor was a criminal. Not only does this stranger give Bruce a sense of how Gotham's people are feeling, he also turns out to be one of Riddler's henchmen at the end of the movie.
With the film focusing on Batman's early days of crime fighting, there's still plenty he has left to learn. By the end, he realizes the needs to be seen as the hero of Gotham, not just a man out for vengeance. But he still needs to better understand the lives of ordinary people if he is to help them and break away from the awkward billionaire he is.