"Have feminist groups been among the most frequent creators of fake news?"
Absolutely. The "fake news" idea if you will goes way back into the 1970's. I believe these early successes that were picked up by the complicit establishment media and repeated without ever looking into the legitimacy of their claims, just strengthened the resolve of these early feminists to create these fake stories to vilify men. As time went on, they created their own fake studies with fake outcomes in order to support their fake "feminist theories", none of which could stand the scrutiny of the real world scientific method.
These stories included this Superbowl Sunday Hoax:
As well as The "rule of thumb" wife beating hoax:
Along with the Mary Koss 1 in 4 rape study deception:
…and a host of others. Feminists continue to fund these “studies” to this very day with the books “cooked” so that the results they want are obtained. Men never come out looking good in any feminist study. That is a given. And it took several decades for the feminist deception to come out into the open. It wasn't until the age of the internet that these 1970's feminists got busted over the truth. In fact, it all still happens today.