When someone reports a crime, to the police or talks about it to a friend, they are believed at face value, whilst an investigation takes place. That is not the same as convicted the accused person in court with no evidence! It's two different things. This doesn't happen with rape/sexual assault. Women are often not believed, particularly by the authorities. For no reason, as there is no evidence to suppose they are lying more than other victims of crime are.
If you went to the police and reported a murder, you would expect them to take that at face value and investigate without assuming you must be lying, trying to get someone into trouble maliciously or whatever.
It is deeply misogynistic to think that women simply reporting that they have been a victim of sexual assault is somehow a weapon to attack men.