I allow my goats to be aggressive to dogs as part of their self defense. We hike on trails where there are lots of dogs, and I don't want to have to chase animals all over the mountains because a dog spooks them.
Larry will rear up and cock his head at them. He's the one who practices for hours with a truck tire swing. Mikey does a hop toward them and taps them with his horns. Diego will actually charge a dog.
When we hike with friends who have a dog, we start out in the trail with the dogs in the lead. Before too long the goats just ignore them and the dogs are turned loose.
We don't have a dog of our own.