It really depends on the age and temperament of the horse. Vida I can get calmed down pretty quick, face the scary thing, see that its not going to eat her and go on.
Younger less confident horses need to be gradually brought around to the scary object. I would never just ride away from a scary object. All horses need to learn that as long as you are there, your not going to let anything eat them. I just keep saying "its ok, its ok" in a calm voice. Circle closer and closer to the object until the horse will stand calmly next to whatever it is.
I have even stopped kids on bikes and asked them to ride back and forth past me. Just for the experience for my horse. The more they can see the less they will be afraid of. The more they hear "its ok" and they aren't eatten, the more confidence they will have in you