With protests rolling out across the country over the purported insensitivity of the new comedy Tropic Thunder toward those with mental disabilities, it’s fair to ask: Are Ben Stiller and the rest of the people involved in Tropic Thunder insensitive?

Perhaps. But not, as the humorless activists claim, for their use of the “R word.” Yes, Ben Stiller plays an actor who once portrayed a mentally disabled boy named “Simple Jack.” But the joke isn’t aimed at the mentally impaired. It’s aimed, like nearly every other joke in Tropic Thunder, at Hollywood’s eccentricities, in this case, the Rain Man/Forrest Gump tradition of mining mental disabilities for Oscar gold.

The real insensitivity of Tropic Thunder is that it raises expectations to fever pitch, then delivers mixed results. There is a lot of funny stuff in Tropic Thunder, Ben Stiller’s first directorial effort since his 2001 classic, Zoolander.

The real laughs—and a clever form of exposition—get rolling early, with a commercial for Booty Juice energy drink and several fake trailers that feature the actors who star in the Apocalypse Now-esque film, also called Tropic Thunder (the making of which is the subject of Tropic Thunder’s spoofery).

Booty Juice’s rapper-turned-actor rep is Alpa Chino (Brandon T Jackson). A trailer for Fatties 2, a film franchise in the Eddie Murphy/Martin Lawrence tradition of fat suits, flatulence jokes and one actor playing multiple morbidly obese characters introduces heroine-addict/bad-boy actor, Jeff Portnoy (Jack Black, whose shtick is growing tired). In the trailer for Satan’s Alley, a Brokeback Mountain-like art film that exchanges cowboys for monks (and hilariously notes the similarity between rosaries and anal beads), the first glimpse is had of Robert Downey Jr.’s character, Kirk Lazarus, a multi-Oscar-winning Australian method actor who, for Tropic Thunder, tries to outdo Robert De Niro’s Raging Bull weight-gain by undergoing controversial “pigmentation surgery” to portray an African-American sergeant. Finally, a trailer for Scorchers 6: Global Meltdown, presents Tugg Speedman (Ben Stiller), a washed up action star who lost all credibility from his role as really not smart Jack in Simple Jack.

The actors, plus a pyrotechnics expert (Danny R McBride—who also stars in this summer’s competing action/comedy Pineapple Express), an insecure director (Steve Coogan) and the Vietnam vet upon whose memoir Tropic Thunder is based (Nick Nolte, looking much like his mug shot) head into the Vietnam jungle where they plan on shooting with hidden cameras in an attempt to lend the over-budget film a bit of vérité credibility. Of course, real-life Southeast Asian poppy farmers think they’re DEA agents.

Back in Tinseltown, Tugg Speedman’s agent (Matthew McConaughey, himself as usual) and studio executive Les Grossman (Tom Cruise) negotiate with the poppy farmers when they kidnap the stars and hold them for ransom. Cruise is great as the balding, bloated, hirsute, dickhead exec who abuses first and asks questions later. That is, until he partakes, indulgently, in the incredibly lame, incredibly cliché “joke” of being a white guy who dances to hip-hop. Jesus, that joke is tired.

Tropic Thunder is well worth watching for Downey Jr.’s Lazarus alone, particularly his interactions with actual black-guy Alpa Chino. At one point, the pigmentally altered Lazarus lectures Chino with a speech that includes mentions of “400 years” and segments from The Jeffersons’ theme song. But Tropic Thunder has a formulaic and softball-satire element to it that softens its edges. Though Tropic Thunder is the best comedy of 2008’s blockbuster season so far, that’s not really saying much. It’s quickly shaping up to be a summer of overachieving comic-book movies and underachieving comics.

Tropic Thunder
Directed by Ben Stiller an written by Ben Stiller, Justin Theroux and Etan Cohen
With Ben Stiller, Robert Downey Jr., Jack Black, Brandon T Jackson, Nick Nolte, Matthew McConaughey and Tom Cruise

Dreamcatcher, Regal Stadium 14
107 min., R