You seem to believe that the Friendship lasting beyond the War being Rare, means that it's not a legitimate relationship to show. It's not like there are numerous "War-Time" relationships shown in Firefly that have so intensely lasted into the after war period, there's just the one, Zoe and Mal. So, why is it poor writing/characterization to explore that unique friendship that lasted beyond the war with your characters? I'm not arguing any of your facts as to the rarity, just the conclusion that to use that rarity is poor writing/characterization. Isn't a goal of good writing to explore the unique/rare relationships/situations?
Indeed it would be good writing for Firefly to have explored the mystery of Zoe's eternal subordination to Mal. The thing is, the episode War Songs merely tries to show that it's due to their shared combat experience. That shared experience certainly explains keeping in touch, even to the point of coming to another veteran's aid. I think there was an episode where Mal goes to help another buddy from the war. What is completely mysterious is why Zoe is still Mal's subordinate, even after the war.
The claim that it's because they're in business together is ludicrous. For one thing, it's not really clear exactly what their business really is. Sometimes it's supposedly just to keep flying, i.e., stay free, which means it's some sort of political motivation, and Zoe/Mal are
not just friends but political militants who never discuss politics and never discuss their political strategy. Other times, it's just to make a living, except fleeing all the time, instead of looking for steady work or even building up a good reputation, makes no sense. What they are really doing is Jesse James in Space, a supposedly peaceable vet driven to a Robin Hood life of crime by the postwar abolitionist tyranny.
The rest of the badly written story is that Mal and Zoe go into the Firefly "business" so that they can keep on doing whatever it is that they are doing, i.e., stay together, not that they are together because they saw an opportunity to make money.
Part of the problem with Firefly fans is that they want to say they like the characters. Good characterization means that the characters have motivations for their actions. They may not be exactly rational from an outside viewpoint but they make sense from the character's viewpoint. When motives are mixed the character wrestles with understanding and acting upon those desires and goals, if only in pursuit of success in achieving those goals. Zoe supposedly loves Wash, who could surely get an honest job. But they stay in a gang so that Zoe can call Mal sir. This interferes with her marriage. Why does she do this? Because they were vets from the same unit? It is not a matter of opinion to assert this is nonsense.
The final defense is that Zoe indeed does not understand herself and that her character arc involves personal growth culminating in an epiphany about the nature of her relationship with Mal, and her subsequent choice. This too is impossible to maintain, because the movie shows that Zoe had barely acknowledged the simple existence of a conflict in her goals for life (sort of wanting a baby,) before Wash was killed off. If Zoe's choice was any part of the dramatic arc in Firefly, this is a huge copout. No, as I said above, it is pretty obvious that Mal's choice between his women is one part of the story. And it's not one that involves good characterization but is, instead, playing with archetypes from myth.
There is no defense of the characterization in
Firefly as good characterization in any recognizable sense of the term. This is not an opinion because it has been demonstrated. Trying to maintain that it's all just a matter of opinion is equivalent to saying there's no difference between truth and lies, because there's no such thing as truth. People are perfectly free to have their opinions but they are not entitled to their own facts. The idea that everything is just a matter of opinion is not a fact. It is a very extreme notion, not just way out in left field (really, how do people like that navigate through life like that, except they don't act upon their purported beliefs?) but deeply, deeply cynical. Since it's just opinion, there is no discussion, there is only agreement, which is nice, or disagreement, which is not nice.
The true logic, of course, is that, if you truly believed what you said, you wouldn't bother posting anything past yay or boo. And you certainly wouldn't be so hypocritical as to get offended over an esthetic "opinion" since there is no objective fact. My best judgment is that it is the clear cogency of the arguments, the demonstration of the fact, that is offensive. Since the official opinon that is agreeable, nice, is that Firefly had great characters, the demonstration of the factual falsity raises uncomfortable questions about precisely what the fans really do like. Those answers are embarrassing, and articulating them is unacceptable because it's not agreeable, nice, and worse, not nice about themselves. The outrage is in effect killing the messenger. Still doesn't refute the message.
PS The funny thing is, Firefly fans don't need to defend the bizarro world characterization in Firefly. It really is a matter of opinion that good writing requires good characterization, if only because a poorly motivated character can still be given great dialogue, and be entertained. And no one has ever managed to demonstrate factually that entertainin is bad writing. Personally, I think seeing a man murder a prisoner isn't entertaining, and this unpleasant experience really kept me from ever engaging with the show. Others may enjoy this sort of thing. That too is a matter of opinion, and I've never argued otherwise. I've just implied it's bad taste.