People still had hope for BvS (Remember, people are still split on Man of Steel.), and that movie wasn't a remake of a beloved franchise where most of the focus is on an extreme shallow and pandering change. Plus, the trailers for that weren't so bad. At the very least they had the good sense to ignore the abomination that was Luthor in that movie and focus more on the action.
The Ghostbusters trailer however, both show humor that falls WELL below the standards of the first two films. (Most specifically, the vomit gag) not to mention the replacement for Winston is such a stereotype that it's almost painful to watch. Then you add in some painful dialog (Such as the characters stating that one of them knows more about Physics than anyone, almost word for word, which breaks the "Show, Don't Tell" rule of storytelling.) Ghosts that look like they came right out of the live action Scooby Doo movies, and on and ON and you have a recipe for "downvotes out the ass" as the AVGN would say.
Also, "a GB3 where Murray was half adding it would be worse then a movie with 4 McCarthy's"? You haven't seen many Murray movies have you? Half Ass is the man's default state of being. It's part of his charm.