I absolutely don't blame you for being upset. You have
eighteen acres for goodness sakes! Shouldn't that be enough to not be bothered?
Anyway, i was just going to make a suggestion for the long term. I'm not a dog person either, but i have found since living in the country and raising chickens - a good dog is priceless. I raise the kind someone mentioned - who barks at people in the driveway, eats table scraps, and pees all over my property so that others don't come around.
I was amazed when we first got a dog because i had a puppy lab mix who wasn't any bigger than a rabbit. But he had peed at the corners of our property. Suddenly, the neighborhood dogs, who used to walk right through our property, almost daily, stopped at the corner of our property, crossed the road and went around us. Apparently the pee was much bigger than the dog.
My dogs are the reason i don't worry about predators or neighborhood dogs. They're not the greatest protectors in the world, but they do get my attention when something is amiss. That and the fact that they don't bother my chickens, makes them perfect to me.
It's just a thought.
In other news, i would absolutely shoot the trespassing jobs if they make evil eyes at my chickens. Sorry, dog lovers. As the OP states, it's my property, and if they can't respond to my yelling at them, or my dogs barking at them, they will be forced to respond to my gun.