I feel like that kind of behavior is unacceptable.
Similar situation happened to me the other day. There are "apartments" on the property where I teach lessons. One of the tenants has dogs, which isn't a big deal usually, the horses are used to the dogs, and the dogs are used to them.
But I was in the arena giving a little girl her FIRST lesson, and this dog who has obviously been cooped up for a while comes bounding into the arena, barking and leaping around. Three other dogs followed, yapping and barking playfully. They didn't mean any harm, but four dogs barking at you is overwhelming! I held the horse while I scanned the area for the owner. She walked out of the barn and just kind of watched. I said, so politely, "Ma'am, would you mind grabbing your dogs? They are really sweet and want to play, but they are spooking the horse just a bit." He wasn't really spooking, but I can't very well continue on a lesson with four BIG dogs running around.
She says to me, "Oh, they'll calm down in a minute, just let them play." o.0
The BO came out and saw what was happening and was like, "Amanda, get your dogs out of the arena! There's a lesson going on!"
At least my BO saw the problem... >.>