It’s not until a chipper spelling-bee competitor named Chaitanya Chopra drops the F-bomb upon an adult’s request that it becomes clear newly minted director Jason Bateman knows how to push the right buttons.

Bateman’s directorial debut “Bad Words” (Rated R; 89 Min.) treads the line between nasty and touching to good effect. It’s a fine balance many directors can’t find even later in their careers, but Bateman chose the right low-key project to demonstrate his directing finesse. He shoots with a filter that approaches sepia; as a result, the movie’s ugliness matches its main characters’.

Bateman also stars in the movie as Guy Trilby, a fortysomething who bullies his way into a junior-high spelling bee because he never technically graduated. He is the definition of an asshole and spends much of the movie making snide remarks to his fellow competitors to sike them out, or having awkward sex with Jenny (Kathryn Hahn), a journalist trying to figure out the method to his madness. She figures out it out about 10 minutes after the rest of the audience.

So no, “Bad Words” isn’t the most surprising of movies. The ultimate reveal gives Guy some humanity, but it’s his relationship with Chaitanya (Rohan Chand) that really drives the movie. Chaitanya’s dad has apparently abandoned him during the bee so that Chaitanya can learn to be on his own; Guy also has some daddy issues. They bond and Guy finally finds someone he can open up to. He’s essentially a giant nine-year-old, so why not bond with someone who’s actually that age?

The two get in to some very appalling, R-rated shenanigans. Yet as dirty as “Bad Words” gets, it remains kind of sweet because these two are clearly bonding. Bateman finds the humanity inside screenwriter Andrew Dodge’s cynical monster. Maybe it’s easier to hit that emotion when you play the main character yourself rather than directing another actor, but Bateman is convincing. It’s a pleasure watching him grow as a comedian and as an auteur — he’s clearly learned from frequent collaborator Jason Reitman.

While dealing with touchy subject matter, Bateman could’ve made the mistakes other first-time director Joseph Gordon-Levitt made in his commentary on pornography “Don Jon.” Gordon-Levitt’s film was too preachy and too focused on basic filmmaking to make any of his points stick. In contrast, Bateman shows maturity and experience, taking a relatively simple script and making the audience root for the bad guy. “Bad Words” is ostensibly about a spelling bee, but it’s the words spoken offstage that have the most impact.