A comedy about immune deficiency is bound to have its protesters, and IMD activists have already waged their war 21st-century style by hiring a public relations maestro to smear Disney’s good name.

The activists could save their money in one of two ways. They could quietly wait for “Bubble Boy” to die the quick death it deserves. Or, they could pool their funds and start a class-action suit with every other group this misadventure manages to slur, including Republican conservatives, Jews, East Asians, South Asians, the elderly, Nebraskans, religious groups, Hispanics, people who like cows, achondroplastic dwarves and the general population of moviegoers.

It’s hard to believe that “Bubble Boy” blew out of Disney factory pipes, specifically Touchstone Pictures (who knows, maybe they’re priming audiences to do a gross-out remake of “Song of the South”). The sad thing, if you can stir up anything other than apathy, is that this so-called comedy actually had irreverence potential. Instead, you feel like you’re wrapped in a plastic bag and, by 30 minutes into the movie, all the oxygen is going to keep your vitals ticking instead of your brain.

Ironically, the actual IMD setup almost has a fairy-tale quality to it, with the vaguely endearing Jimmy Livingston (Jake Gyllenhaal) explaining his condition in voice-over narration. After a four-year hospital stay, his plastic confines at home take on the feel of a private castle. He values the smothering ministrations of his religiously manic mother (Swoosie Kurtz), who is determined to keep more than germs away from him. Kurtz has some prize moments, like reading her son fables that end with people dying from germs if they leave their home, or taking a high-pressure hose to neighborhood boys taunting Jimmy outside his window. Jimmy’s not just trapped in a bubble the Livingstons in their Palmdale subdivision of Dante’s Inferno have deliberately caught themselves in a ’50s time warp.

All that comic promise takes a nose-dive once Jimmy leaves for his cross-country bubble-suited pursuit of Chloe, the girl next door and best friend (Marley Shelton) about to marry the wrong man. Set for Niagara Falls, he hitches a bus ride with a religious group in which members are named Todd and Lorraine and the head guy is Fabio. After he gets dumped in the desert for his wide-eyed assessment of them as cult members, he meets knife-wielding Mexican bike rider Slim (Danny Trejo). The stereotypes don’t get much better in these encounters with the detritus of Americana, including we kid you not a trainful of real “freaks” cowed by their foul-mouthed overseer, Dr. Phreak (Verne J. Troyer, best known as Mini-Me, Dr. Evil’s protg in the “Austin Powers” sequel).

Amazingly, “Bubble Boy” actually bucks a movie trend by being largely flatulence- and poop-free, considering it’s aiming for the adolescent male crowd. Instead, it goes straight for the bully humor by making fun of religion and race, even as the film holds up Jimmy as the symbol of wholesome, likable purity. The occasional funny gag, such as the Indian who drives an ice cream and curry truck, are rare in a soup of predictable jokes almost too dull to be offensive. “Bubble Boy” isn’t so much a plague to be avoided as a low-level virus you can really do without.