In my 20s I went to a private adult Halloween party dressed as a Vampire's victim. Two puncture wounds on the neck, white make up, slightly tatty Victorian style nightgown, with "Vampire" boyfriend in tow. A standard Gothic trope.
It's perfectly clear that what the OP and others are expressing concerns about is not that sort of thing.
And the OP raises a good point. It has taken years for rape victims to be taken seriously, rape within marriage was only outlawed in the 90s I think, and thanks to a society that saw women as possessions and objects in legal terms for centuries, it has taken too long for people thankfully unaffected to realise that not all victims look the way people think they should. This unpleasant "trend" harks back to those standards and that if there's no obvious signs of violence they might be lying or couldn't have fought back hard enough.
The more I'm thinking about it, the angrier I feel. It is something that should examined and nipped in the bud, especially with the increased awareness and proliferation of VAWG. And I'd feel the same about similar if it concerned male victims, whom I aware do exist.
There should be limits in society. I'm pro freedom of expression in many ways, and not unfamiliar with edgy lifestyles chosen by hopefully fully informed adults. As mentioned, I've dipped my toe in the fetish scene, but it's been in adult environments, carefully controlled with no photography and strict rules around consent. It's never going to be entirely without risk, but adults are allowed to make their own decisions about exposure to risk.
Children can't.
The "pearl clutching" insinuations are unnecessary. There should be a line drawn somewhere, and costumes on children that mix subtle titillation with violent themes that pose a real life risk is it, IMHO.