All beliefs are subjective, Velveteen, even professional ones. That's kind of the thing about belief. Just because it's institutionalised sexism rather than sexism at an individual, personal level, doesn't stop it being sexism. What we have here is an institutionalised belief system ("It's harder to get a rape case past a jury than a mugging case") based on the entrenched misogynist views of society as a whole ("women are more likely to lie about rape than people of either sex are to lie about mugging.")
Adding the adjective "professional" makes it sound like it's suddenly an objective thing, but it isn't.
What we're wrestling with is the continuing idea that "there are no witnesses to a rape, just her word against his" because women aren't allowed to be believable witnesses to the crime committed against them. Unlike a mugging down a dark alley where the victim is allowed to be a believable witness to the crime committed against them. This appears to apply even when the victim emerges from the encounter covered in bruises with strangulation marks round her neck ("She liked rough sex...") or was drunk and unconscious ("I tripped and fell into her vagina, m'lud" - yes, that is a real case, and yes, the guy did get off).