Probably the same crowd that thinks Dean "forces" Sam to hunt and that Dean just guns down every monster he sees (and this in itself is oppression toward Sam for being a monster himself of course) no matter that believing this requires substantial mental rewrites of the show.
Hunting is vigilantism, which can be either better than, worse than, or the same as "being a cop" depending on your perspective on that vigilantism and whether you think that vigilantism is borne from the failure of government institutions to actually serve the downtrodden people they're supposed to protect (see: public response to UHC vigilantism) or whether that vigilantism is Barney Fifedom rooted in profiling for which we criticize policing as a government institution. It's not as simple as saying hunting is one or the other.
I think the opening seasons of Supernatural present Sam and Dean's hunting vigilantism as the former. Especially through Dean's early established resentment for the incompetence, obstinance, and corruption of cops and their frequent profiling of him as a drifter (1.01, 1.03, 1.05, 1.07, 1.11, 2.07, 2.12). Cops are also a direct source of episodic villainy from early on (1.03, 1.11, 2.07, 4.06, 6.03, 9.15, 10.22). I suspect that one could easily make a case that Dean's early resentment for cops also comes from a belief that most law enforcement has to have seen a weird case or two in their time and turned a blind eye, and that Dean sees this willful ignorance the same way we see things like backlogs of thousands of untested rape kits and shoddy detective work that occurs due to profiling of the victim and general apathy over what happened to them (we also see this directly in 7.03 when cops don't care about Amy's victims because they were petty criminals or addicts). I think this also meshes well with Dean's resentment for gods (or those with power equal to those of a god) who are aware of the suffering of people around them but do nothing to stop it (see: Gabriel, Chuck).
Of course, in season 1, Sam and Dean mainly deal with ghosts, curses, and several human villains, which is a bit different from dealing with living "monsters". Season 2 then begins to explore what it looks like for Sam and Dean to meet other hunters and other people in-the-know who might have a different perspective on vigilantism and make assumptions about guilt rather than bothering with actual detective work or alternative solutions, and the Winchesters reactions to that (overwhelmingly negative) and their own perceptions of what they do and what kind of rules they need to enforce on themselves going forward are explored (we see this first with 2.03, but it's essentially a theme of the entire season. We also continue this in later seasons with 4.04, 8.09, etc). Post Gordon, Dean displays a significant distrust toward other hunters out of concern that they do not share his beliefs and might try to harm his brother and other special children who don't deserve it (he doesn't even trust Ellen for most of season 2 and even accuses her at one point of floating their location to Gordon).
That said, a strange assumption developed around these sorts of episodes—that supernatural entities are always intended as a metaphor for the oppressed when that's rarely the case. The majority of cases in Supernatural involve villains (human and non-human) behaving as oppressors in the story who use their power to exploit the vulnerable. "Monsters" just trying to get by just happen to be the cases that stick out to us the most. Take vampires for example. We think of SPN vampires and the first people we think about are usually people like Lenore and Benny, both of whom are profiled and targeted for violence by trigger-happy hunters. The story of these episodes ends up being "don't be a cop". But the next time a vampire appears, an audience member sometimes can't shake the belief that vampires are eternally tied to this lesson despite all evidence to the contrary. Vampires don't always happen to serve the story in the exact same way every time we see them. The vampires in 1.20 are clearly implied to enjoy sexually molesting their victims for their own sexual gratification. Boris's operation in 6.05 is very clearly intended to parallel sex trafficking (of young and often underage girls he has exploited online and lured to locations where he can kidnap and feed on them). He is also heavily implied to enjoy raping the people he's turned.
Boris and some other groups represent oppression of humans by supernatural entities in ways that are also heavily organized. Demons whole operation revolves largely around exploiting people who are poor, grieving, and/or traumatized and desperately in need of escape. The angels frequently refer to humans as monkeys and largely see hurting and using them in any way they wish as their birthright. The Stynes are a powerful family who has used their wealth and influence to silence opposition and prey on others to increase their own power. The alpha vampire is exceedingly wealthy and powerful and exerts wide spread influence on vampires, and directed Boris's operation (and others) where people were forcibly turned in droves (he's also heavily implied to be a pedophile). The Leviathan take over seats of political power and wealth in order to establish control and feed on those beneath them on the social ladder. There's nothing screaming "oppressed class" about any of this, however much groups like the angels for example might cry wolf while behaving as oppressors. Their behavior in particular is quite reminiscent of the ruling class placing blame for all of societies ills on the poor.
Supernatural does deliberately (and sometimes accidentally) explore themes surrounding "not turning into a cop", but it also explores monsters as a metaphor for the ruling class and Sam and Dean as representatives of the lower class rebelling against and providing others with protection against powerful forces misusing their power and preying on those weaker than them, and I think sometimes people want so badly for SPN to fit their mold that they get really lost in the weeds and simplify it down to something it isn't and it becomes much more dull than it really is.
Also since this is clearly a samgirl take and I have to: Sam defends cops more than anybody, doesn't trust Sonny because he's an ex con, and said people in jail probably deserve to be terrorized by a ghost.