Because this movie has become an utter mess on the Internet. The whole premise from the movie studio, and what they originally told people before telling them anything else, is that it's "Ghostbusters with chicks." And because that's what it is, and *some* jerks did get sexist about it, now *any* criticism of it is being fluffed off as if they're just sexist and hate it because it has women.
And you have sites like the above which are fueling that mess. And people did the same with the large number of dislikes, claiming it was only because of gender, not because people might actually have any of a dozen other reasons to not like the trailer. (Meanwhile, CoD:IW, with almost a complete lack of women in its trailer, has almost four times as many dislikes while still having about ten million fewer views.)
It's a disaster for honest discussion, and this is the perfect example. You can't criticize the movie or anything about it without people trying to find some way to call you "sexist." And yeah, there's people who are sexist, but there's so many people out there who aren't liking the way this looks, and it has nothing to do with gender. There are *women* out there who don't like the way this looks, but somehow they're anti-women, because... well, because the Internet is stupid, and the recent attempts to act "enlightened" have led us to this.