It's like when fortunate sons play Fortunate Son at political rallies. Or when people get mad about Rage Against The Machine getting political. I'm not one to gatekeep comics, but they should at least skim the wiki to see the Punisher's origin story.
Granted, I'm not super into comic books. But the Pushisher is a vigilante that likes to solve crime in a pretty brutal way. And, IIRC, he doesn't necessarily care if the person is guilty, only that he thinks that they are "bad" in some way, and for that, they deserve whatever torture and brutality he dishes out. Cops flying a Punisher flag is not ironic, it's on the nose.
Everyone gets that he represents the brutality of the justice system. It's just that most people in the justice system don't see his behavior as a fault or criticism; just reality.
No, if you've read the Garth Ennis run of The Punisher then you would know that cops wearing punisher shirts is completely misunderstanding the character.
Like a lot of people, you have an idea of the character which is not the definitive version of the character.
If you read the Punisher and you come away from it thinking that vigilantism, murder and so forth is good then there is probably something very wrong with you.
I have a working theory that mass appeal ruin the original content.
To your credit, as a non-Punisher patron of geek arts, you're probably right. The spirit of the original comics is likely expressing a deeper message than most people could understand from a cursory glance and watching one of the dumbed-down movies.
To your discredit, the population at large generates a mythos that transcends the character and strips away all sense of subtlety. To anyone who doesn't know the comics intimately, The Punisher is a guy who's like Batman with more brutality.
And, at the risk of redundancy, I'm convinced this is true of pretty much any character, fictional or non-: caricaturization of their greatest qualities, then memorialized as a god of [subject matter expertise]. The _only_ time I've ever seen a deviation from this is when a character is hard to place because they're all over the map (e.g., Ben Franklin, Christopher Lee).
My main exposure is from his Netflix Marvel show appearances. It's been a while, but I do distinctly recall thinking he went easy on the people involved considering what they did.
> Everyone gets that he represents the brutality of the justice system.
I mean, The Author Is Dead; this is a fair interpretation. But I'm skeptical that the kinds of police who put a Punisher skull on their uniforms feel this is some kind of Full-Metal-Jacket-duality-of-man commentary as opposed to just fantasizing about murdering [who they imagine to be] criminals.
I don't think people get mad at RatM for being political so much as they mock Tom Morello for essentially trying to sell revolution as a lifestyle brand, and generally engaging in performative politics that don't seem particularly congruent with how he lives his life.
Zack de la Rocha and the others don't typically receive the same criticisms unless their actions are lumped in with Morello's under the banner of "RatM did X".