solarpunk memes

I assume they mean "murderer of fascists?"

A fascist is someone who supports a single strong leader with total control of the nation. 'Dictator' was an actual position in the Roman Republic; the people could vote to give one man absolute power for a period of time. Makes sense if you're dealing with a natural disaster or invasion and don't have time to go through the usual channels. Fascism became popular in the chaos of the post WW1 era. Things were changing rapidly, and conservatives wanted to rein in the 'undesirables.' Ironically, the Communist Russian Revolution was a huge spur to the creation of numerous fascist parties across Europe.

Frank Castle, the Punisher, is not a fascist. He isn't interested in taking power for himself, and doesn't want a dictator. He often speaks of having the greatest respect for Captain America, the guy who always chooses the side of liberty and fair play. Frank knows that he's a criminal and a murderer. He just doesn't care. IMHO if he and the Joker were both locked up and unable to kill each other, the two would get along fine.

How fascist he is depends on who is writing him. His symbol is literally a stylized Nazi totenkopf, and while he has never voiced support for totalitarian leaders, his solution to crime - escalating the violence - is consistent with fascist ideology.

I don't really see how he could be construed as one, other than the kneejerk "fascism is when bad things".

The whole point is that he's not like cops.

I don’t know where the US fits in your consideration of corruption but cops very rarely go to jail here, even (especially?) when they form up around a symbol. Here’s one example: the long-lived murderous LA Sheriff’s Department gangs. https://knock-la.com/tradition-of-violence-lasd-gang-history/

That's how it usually works. Consider Donald Trump.

I mean, to me the meaning of that juxtaposition is pretty clear.

The Gadsden flag highlights individual primacy, but the thin blue line sticker makes it clear that it's his individual primacy that he's concerned with. For an anti-authoritarian evoking that symbolism, the 'me' refers to the general autonomy of humanity or at least Americans, but in this case it probably literally refers to that specific individual's autonomy or to the autonomy of the United States as a country in a nationalistic sense.

He's basically just representing his subculture and thumping his chest about how nobody better tell him what to do or get in his way, while also showing that he's affiliated with a big gang. Whether he's aware of the racist speech the symbol is referencing or the symbol's deeper meaning is kind of up in the air, but it still probably wouldn't produce much conflict with his sense of nationalist autonomy in an authoritarian context regardless.

Honestly, it's that context that I think makes the association with Punisher inevitable. Whether the character supports the current gang in charge or not, he clearly believes in an authoritarian model of crime and punishment; that's the lens he views the world through and the impetus for his actions. If it's satire, it certainly doesn't read that way. Though, to be fair, the show is probably a lot more egregious in that regard than the comic (while also likely being more widely consumed).

Frank Castle supports authoritarian measures so much that he goes beyond what the legal system allows for. He literally names himself after an action designed to reinforce authoritarian hierarchy. Sounds pretty on the nose to me.

100% - welcome to SLRPNK and our culture of signal boosting and solidarity.