Alrighty, I see both sides of the coin, for I have had horses most of my life, and have ridden both mtn and road bikes. Now, when I was a lass... read stupid and young, I would go galloping down roads blindly and nearly killed a few bikers... similarly, bikes are quiet and super fast, and, to a prey animal, they are potential monsters. Horses do see nearly behind their heads, but they haven't evolved to deal with things like bikes, and their genes tell them that if something coming up fast and quiet behind them, it is probably to eat them. Horses, are big and we need to remember that they can move in all directions very quickly. Non-horsey people frequently fail to recognize this and get within strike range very readily. This makes the riders (of the horses) understandably nervous. If my horse kicks you even if you invaded her space and scared the #$%^ out of her, I am liable. For this reason, horse riders tend to come across as grumpy with bicyclists. Aside from crazy teenager equestrians (there's no helping them), most horse riders and cognizant of what is going on and they want to avoid dangerous situations. Trail ettiquete is to dismount or just stop so a horse can go by. Even if you are in a pack. This is just how it goes... sorry. Though, I as a rider, if I am riding a solid mount, will either move off of the trail or to the side so a bicyclist can calmy and quietly go by. It's good if the bicyclist talks to the horse so the animal can understand that it is a human on the bike. It's just a difference in language... we can all get along if we all try