Seriously? Why breed bash? Was it necessary to use "pitbull" as the dog that "mauled" another dog? The media does a good enough job sensationalizing "pit bull attacks," does everyone need to do it?
As for the OP, the important thing is that the boarder specifically ASKED that her horse be separated, and it was put with the other horse again without being discussed first. I would leave.
Just for the record here, pit bull attacks are sensationalized because when a pit bull attacks it does serious damage......compared to the little chihuahua who nipped a toddler.....the attacks by pitbulls can be horrific, that is why the media reports it.......ie. 70 year old woman mauled, receives 189 stitches....I think that's newsworthy.....I'm stating a fact, not bashing a breed....because there are many other breeds out there that can do as much damage when they attack.....