I love all dog breeds and it's not the dogs fault they act like this... It's the owners fault. The dogs were never trained to act right. I have a red nose pit mix and she's a sweet girl,but she knows all birds are off limits. She actually watches them for me, her favorites are the Polish.
I'm sorry you lost your chickens and I'm sorry that you have to deal with neighbors like this.
training if a dog helps, for sure. But, they still have inherent instincts. So, it is simplistic to think that only the dog owner is at fault. There are dogs that act badly/can’t resist their prey drive despite much training. In any event pit bulls ARE strong and large and can seriously harm a person or animal. Add in running in a pack, and it can amplify that. Comparing your well trained single dog to this situation isn’t a great comparison. I’m glad your dog is smart and well behaved and a good help to you!