I've never set foot inside a pf.

This is clear. I used to be anti-planet fitness. In the fitness community there is a whole mess of hate towards pf. Claims like "there are no free weights" are clearly untrue (unless others are radically different from the few I've been to) and being against fitness seems doubtful after frequenting one.

The main point I see from you is "they kick people out for being healthy." And I have seen about 4 cases of this. Each follows the same pattern, the customer claims to be ejected for being thin, planet fitness claims they weren't following the dress code, fitness people make a bunch of videos about how evil pf is. It is completely possible they enforce the dress code haphazardly, but as far as my experience and their website, there is no policy against being fit.

The combination of the phrases "No judgement zone" and being "anti-lunk" really mean "this gym is not for gym rats." They will let anyone sign up, you can work out, but understand this isn't a normal gym.

It's like if a bar near an university didn't want college students, they could advertise as "drinks for everyone" meaning locals are welcome and still have a "fraternity gear" alarm. Having rules like, no greek letters on clothing, no hats and no shorts could dissuade college kids who do go to that bar from acting like college kids. Having little to no jagermeister or red bull ensures that it shouldn't be a regular hang out for college kids. But sometimes people don't get all the hints and decide to make a place fit their ideas, then the owners start kicking people out.

Every case of "discrimination against health" I've seen involving pf sound like there is something else happening.

It is perfectly ethical to court a particular demographic and keep that demographic happy.