Of all the people whose ire you might actively seek to provoke, you’d think the ones who can bench press 500 pounds would fall pretty far down the list. Not if you’re on the marketing team for Planet Fitness, the rapidly growing national health-club chain that has recently declared war on bodybuilders. In a ubiquitous series of television commercials that debuted last fall, the chain openly mocks those brutish gym rats who grunt and flex their way around the weight room, alienating everyone around them.

Maybe you’ve seen the one where a greased up Schwarzenegger-type swaggers through the gym repeating the mantra, “I pick things up and put them down.” Or the one where another “lunk”—that’s what Planet Fitness calls these sorts of people—struggles to tie his shoes. A third shows a screaming gym buffoon as he fills out a membership application, flexing and making sound effects as if he’s maxing out on the squat rack. “Not his planet, yours,” reads the tag line.

Pretty funny stuff, right? Not to the bodybuilders and serious weight lifters who find the way they’re portrayed in the commercials offensive and the way they’re treated in Planet Fitness clubs quite possibly discriminatory.

I’ve felt that discrimination myself firsthand. I’m not what you would call a bodybuilder, mind you, or a regular Planet Fitness member, either. But I have been to number of different Planet Fitness locations in the past few years, mostly as an “emergency gym” when I’m traveling. (The fact that I even have an emergency gym should tell you something about my approach to working out.) In some respects, it’s not a bad place to lift weights—very clean and quiet, and set up in an unusual yellow and purple design scheme with painted signs reading, “Judgment-Free Zone.” No one will judge you, presumably, if you partake of the bowl of candy on the reception desk, or of the weekly Pizza Mondayspromotion. (Yes, they serve pizza in the gym.)

Then there’s the fact that certain bodybuilding exercises—like dead lifts and clean-and-jerks—are prohibited. CEO Mike Grondahl has further promised, “We’ll be the only fitness chain that can say we’ll never try to sell you personal training. A lot of people will say we are dead wrong with this historic move. But the world was flat once, and who the hell needs a friend for 50 bucks an hour?” The facility also comes equipped with a “lunk alarm”—a siren that is supposed to go off whenever someone grunts too loudly or drops a heavy weight on the floor. (The latter is a moot point at most Planet Fitness locations, where they don’t even have any large weights.) I’ve never set off the alarm, but on more than one occasion, in different locations around the country, I’ve been lectured by staffers for breathing too hard when lifting, and I’ve gotten dirty looks for excessive sweating in the weight room. Clearly it’s not my planet either.

(Nor is it this guy’s, a Planet Fitness member who claimed last week that he had his membership revoked for making a video of himself flexing in the locker room. Sorry bro, they kind of have a point with that one.)

I’m not the only one who’s noticed this assault on people who are actually trying to get a workout. Men’s Health called Planet Fitness “The Worst Gym In America,” and over the past few months, my comrades-in-(big)-arms have been speaking out against the chain on blogs, in bodybuilding forums, and at the websites of weightlifting and health-club magazines. In March, a group of lunk activists successfully banded together to have the Planet Fitness You Tube channel shut down by organizing a mass flagging of their commercials as offensive material. The chain was forced to start a new one, under a different name. And other gyms have started making their own commercials in response to Planet Fitness.

“It was the revenge of the lunkheads,” says John Craig, a Planet Fitness spokesman. In cases like this you might expect a corporate brand would back down from a perceived slight to potential customers, but that’s not part of the PF business model. If anything, they’re redoubling their offensive, on the theory that any blowback from the musclehead community will only bolster the company’s image with its core customers. “The guys in the commercials are like caricatures of steroid-addled muscleheads,” Craig says. “We think if you’re using steroids, and prancing around the gym, that you’re fair game.”

The strategy is working. “It’s just a Curves that allows men,” wrote one critic on their Facebook page, referencing the hugely successful, if not quite competition-level, women’s gym that has some 10,000 locations around the world. Planet Fitness, for its part, has been one of the fastest growing players in the fitness industry over the past couple of years, with 422 clubs in operation and around $150 million in annual revenue, according to Craig. Those numbers put the chain in the company of other big industry players like 24 Hour Fitness and Gold’s Gym.

Although it seems paradoxical—like setting up an all-you-can-eat buffet with a “No Fatties Allowed” sign—there’s a lot of money in tailoring a fitness club to people who don’t actually want to work out. The percentage of Americans who belong to some sort of health club has been holding at 15 percent for years, according to Stuart Goldman, managing editor of Club Industry, a magazine for fitness-business professionals. That’s left companies looking for new ways to tap into the doughy majority and capitalize on casual exercisers.

Planet Fitness isn’t the only chain that’s working this angle. Many others have lowered prices, scrapped long-term contracts, and ramped up their programs for children, who comprise one of the fastest-growing demographics in the business. Another industry trend: Cordoning off the weightlifting areas from the cardiovascular machines. If you’re not going to kick the lunks out altogether, you might as well hide them in the back.

“Planet Fitness is run by smart businessmen,” says Meredith Poppler, vice president of industry growth at the International Health, Racquet and Sportsclub Association. “There are thousands of average Jane’s and Joe’s for every big lifter. Many of those Janes and Joes are intimidated by grunting and 50-pound dumbbells. So, they decided to cater to the thousands at the expense of a smaller segment. It seems to be working quite nicely for them.”

So it does, but should we take the success of special-interest gyms like Planet Fitness as a welcome shift in the culture of exercise? Or could it represent a sad departure from the one-size-fits-all health clubs of old?

We’ve already seen how the echo chamber of Internet news helps us to ignore any opinions or facts that we don’t want to hear. What if something analogous were to happen in the fitness world? Imagine if every group had its own place to work out—a gym for muscleheads, a gym for fatsos, a gym for vegans, a gym for Slate readers. The pursuit of health might succumb to its own form of groupthink.

Sure, no one likes it when a loud, aggressive dude is intimidating people in the weight room. But there may be something to learn from living (and lifting) in the sweaty melting pot of American exercise. Even the most odoriferous lunk might have something to teach us, after all—whether it’s a reminder of what we’re trying to avoid, or a reassurance that it’s possible to max out. Ultimately we all have to share the same planet. Sharing the gym might be a good place to start.