Herbebollox,
You state these truisms that a man should understand "X" and be sensitive enough to realise when a woman does not want sex. And also that most reasonable women will not accuse a man of rape when they have not been raped. All undeniably true. Most women and men are reasonable and, luckily, most of us manage to remain in relationships all of our lives without either having been raped or being accused of rape.
The courts are there for when normal social interaction has broken down, to test whether a man has been guilty of criminal behaviour (rape) or has been falsely accused. This is exactly the same as for any other crime.
I don't think there is an assumption that a woman is in "a state of permanent" consent. I have no idea where this idea comes from except, maybe, that, as discussed above, not having consented is hard to prove in the case of rape which does not leave an objective mark of violence and, especially, where two people have already had consensual sex. The point is, as reiterated time and time again, that in criminal law the burden of proof is "beyond reasonable doubt". I seem to remember asking a lawyer what this amounted to (in a general discussion about crime) and being told it was a 95% probability. That means that even if one assumed that 92/100 women were truthful about being raped, you would still need further corroborating evidence to convict. That is not equivalent to assuming women are liars. In addition, if all it took to convict a man was an accusation by a woman (which seems to be what you are actually suggesting, as it would certainly be 100% impossible to prove consent was given), you would go back to the days of the Salem witch hunts, but in reverse.
Juries are, I would guess, at least 50% women. I cannot see why women, many of whom have been victim of rape, would empathise with a "man in a suit".
Rape is vile. Deliberately trying to send someone to prison (to also probably suffer rape) is also vile. The latter may be rarer than the former but that does not mean it does not happen or that courts should ignore the possibility. Human beings of both sexes are capable of dishonesty and causing harm.
I do not know why you have changed my "having sex" into "fucking someone". Is that how you view normal consensual sex?