So a magical girl suffering defeat harms the dignity of all magical girls, but the organization (allegedly) run by magical girls hosting a ppv live stream of a girl being raped to death doesn't? I know I'm overanalyzing an ero manga, but I feel like the plot would make more sense if the trials and punishments were carried out in secret. The punishments are so ludicrously cruel and enough of them are done publicly that average people should know how heartless the organization is.
If you didn't overanalyse, then the answer is every punishment is a specific hentai bad end trope. As ridiculous as this one sounds this time in comparison to the others, it's a pretty 'normal' bad end for the genre, no?
But if you do want to get into it, then I'd say the difference is the dignity of magical girls versus the dignity of a known failure like this. By specifically doing this to her in this context, they emphasize that she is different from other magical girls, only she is at fault, only her dignity is on the line.
The whole court system is actually set up just for that purpose. Its very public, the transgressions of the individual is emphasized. There is zero ambiguity as to the cause, instead of the murky discussions that can form in public. The system exists to protect the reputation of magical girls on the whole, at the cost of (usually unfairly) sacrificing individual ones.
If they did it in secret, then it becomes ambiguous again. People can claim the magical girls are keeping the sentenced girl quiet and out of the way while pretending to punish her. Magical girls would been seen as having no accountability...even if the public's idea of accountability is unreasonable to begin with. It's ridiculous and unfair in the first place that a group of young girls have to risk their lives and chasity so that millions of other people can just go about their lives with no obligations or price to pay other than maybe a bit of taxes. In a pre-modern society they would literally be the rulers of whole nations in exchange for that.
As Yuuri says, true justice and the law aren't necessarily the same thing. So if not justice, then what's the purpose of the law in this case? It does, in fact, protect magical girls...as an institution that is. This is not the same as real life. Sometimes sentences are handed out in modern courts as deterrence, but for the most part the system is (at least on paper) intended to apply correction to individuals, and protect society at large and not any particular institution. Under those principles, then there is certainly no reason for a punishment displayed publicly.
This of course gives our defense attorney an out for her cases. Ultimately, the trial's format also works in her favor...specifics of the law aside, all she has to do is very publicly prove the magical girl, as an
individual, was not at fault, on purely a cause and effect basis. By the way, that's subtly different from having "no choice but to lose". The latter is still her 'fault', even if unfair. Yuuri has to prove not only did the girl have no choice, but that the loss really had nothing to do whatsoever with the individual's choices, decisions, personal circumstances, and even her skill as a magical girl, like when she proved one of the previous magical girls was let down by faulty third party equipment.
Though it looks like this particular case might end up differently. It looks like they're angling towards a one-off where yes, the magical girl did indeed choose to surrender, but the court can't sentence her without admitting that they, the representative body of all magical girls, allowed themselves to be manipulated by an evil organization. Which would defeat the purpose of this system.
TLDR: These aren't punishments. They're excising's of unfitting individuals. Defense isn't proving innocence, they're proving that magical girl reputations aren't affected.