If a burqa-clad young Muslim woman tells you that only being seen by her husband makes her feel sexy, you don’t believe her. You say she’s been brainwashed by her cultural upbringing. She has Stockholm Syndrome.
Why would you think any differently if a young Canadian woman says that dressing as a slut is “celebrating her sexuality”?
Poststructural literary analysis is based on the “death of the author”. It doesn’t matter what the author claims or thinks they’re writing about: what matters is how people interpret it. Authors do not have a priviledged position with respect to their own work. If someone writes a novel that’s obviously about young Hitler but claims that’s not what it’s about, who cares what the author says?
So when I “read the text” that is a woman’s slutty Halloween costume, I don’t care what she claims she’s doing. In fact, I’m less likely to believe her analysis: she’s too close to the material to read it critically. She has too many incentives to convince me that she’s not being oppressed. I also don’t care what people who benefit from a slutty world say.
Sex-positive feminism may be possible, but it needs to be backed in theory. It’s not enough to just say “I’m sex-positive and I’m a feminist!”