The two hashtags are not mutually exclusive. They're both extremely true, and both should be fully respected by non-douchebags of all genders. The situation arises fairly simply, really:
A small number of violent people are forcing potential victims to act AS IF it were everybody out there that was violent as well, because they don't know ahead of time which people are the actual small number of violent ones. Rapists and the lot necessarily cause and lead to awkward interactions between various perfectly good hearted people. And we should be blaming for this... rapists. Only.
The classic metaphor is a plate of delicious home-baked cookies, one of which is laced with cyanide. 95% of them or whatever will leave you warm and satisfied and loved and happy and thinking of your childhood, and 5% will kill you dead. Do you eat a cookie from the plate? Probably not. A small number of cookies would force all of us to treat all the cookies to some degree as poisonous. Is that the good cookies' fault? No. Is that the cookie eater's fault? No.
This could be understood and accepted by everybody, without the need to ever blame or shame either the large majority of decent women or the large majority of decent men. The only people that need blaming are the sole source of the problem: murderers, rapists, flagrant harassers, people who aid and abet them, etc.
This doesn't seem complicated to me. It's not even at all exclusive to sexual crimes or misdeeds. It's true of ANY crime. I have to put locks on my doors and treat all my neighors as potential criminals at first, because 1% of neighbors are burglars or vandals. I have to go to the airport 2 hours early because we have to treat everyone like they might be a terrorist, due to 0.0001% of them being terrorists. Etc. etc.
Honestly, I'm fairly baffled why any of it is contentious at all. Why do we need hashtags? It should be common sense. You don't see anybody putting up hashtags about burglary or home invasion called #NotAllNeighbors or #YesAllHomeowners