I think what you don't understand is that nobody is against the idea of a different perspective. we're not against batman being killed off in a story.
that being said, this short movie is really stupidly written, filled with bad characterization, and only aim for shock values.
I fail to see how having batman being raped by a nobody he sent in prison just because he was on a crime scene is inventive.
No, you're focusing on the wrong element.
The concept of the rape is a bi-product and a conceit for the story being told.
The inventiveness and entire point of the film is in the examination of Batman's hubris, which is a territory where most Batman stories don't actually go because then they get accused of being out of character...and yet the concept itself, the idea of responding to personal tragedy by creating a physical manifestation of the super ego in the desire to forever maintain the control Bruce didn't have that night...is absolutely fertile for any and all scrutiny.
So at the beginning of the film, he is "Batman," quotations intended because he's fulfilling the obligatory role and standing on the pedestal fans and, in the case of this film himself, put him on. He's powerful, he's imposing, he's spewing Keaton-style one-liners and the addict confirms "I'M the coward, YOU'RE the hero." All of this is deliberate...exaggerated by the irony that his pride and over-confidence makes him vulnerable and he's brought down.
Once captured, he's posed like a statue or award figure. He's the persona, the ideal and he's bound (chained) to that, refusing to allow himself to be human. He's not human...he's not capable of making mistakes...he's perfect.
This symbol of perfection is brought to a head by the fact that Batman's awarded "Gotham's Man of the Year" but irony strikes again with the brutal reality. Fans make the mistake of putting Batman on that pedestal when what really makes him fascinating IS his humanity and fallibility, because it's great to see him come up against obstacles and overcome them.
That said, this is clearly taking a darker turn by NOT allowing Batman to win and again, I feel that's a deliberate choice when one observes the film as a cautionary tale against hubris.
The minute Batman starts feeding into his ego and the persona, thinking he can do no wrong, is the minute that mistakes are made. This film not only creates a scenario where that, in fact, does happen...but it takes it to its extreme conclusion by not allowing Batman off the hook and having him pay for it with his dignity and ultimately his life.
I'm fine with that because again, the entire point of Batman and other serialized characters is that their essences are durable and afforded artistic liberties and skewing.
Now do I agree with the idea of Batman being anally raped? No.
But I'm not throwing my hands up in the air over it or saying it's not Batman because I've done one of two things as a responsible audience member...I've either tapped into the filmmakers' intentions and recognized what they're trying to say regardless of how they're saying it or I've found meaning in their work for myself that justifies the means to that end.
Besides, the character isn't one omnipotent thing. It can't be ruined by the efforts of individual creators. Adaptation isn't actually adaptation at all. It's the process of creating a separate, alternate iteration that will follow its own path of circumstances and destinies.
We have multiple Batman's. One had his parents killed by the Joker ("Batman"). Another went into exile for 8 years ("The Dark Knight Rises"). Another discovered that Selina Kyle was a witness to his parent's murder ("Gotham")...and this one pays the ultimate price for his vanity and pride.
They're all Batman in as much as framework. What's fascinating is seeing what the individual filmmakers, writers and artists throughout history do to contort, manipulate, even break the character within that framework.