Are you sure about that? Because from what I've seen & heard the outrage was about the fact that the trailers made the movie look like complete dogshit.
That fact that it had an all-female cast were the least of people's outrage about the movie.
Are their some people out there who hate the movie because it has women in it? Absolutely but does that represent the majority of people who don't like Ghostbusters? Absolutely not.
There are several groups who are angrily opposed to this movie:
1. People with an alt-right mindset who see this casting as an SJW-feminist stunt and want it to fail because they're misogynists who can't relate to female protagonists. Some of them are Ghostbusters fans.
2. Fans of GB who wanted a sequel rather than a reboot, didn't care about the gender, but don't like this comedic creative team (Feig-McCarthy). I have some sympathy for this group, as most GB fans wanted a Ramis-Aykroyd sequel, but it seems like this film is solid so time to let it go.
3. There are folks who claim to be GB fans, but don't want any more GB in any form. They think it should be left in the past, regardless of the high quality of the cartoon, videogame and comic series in continuing the franchise. Usually these people don't have the same issue with Marvel comic book sequels or Star Wars. So their argument kind of falls apart and they fall into one of the first two camps.
Point is, the film was getting hate well before the trailers.