I would be livid if someone was forcibly trying to breed their dog to mine. I would tell them to keep their dog off my property or I'll shoot it, I wouldn't really shoot someones dog but people need harsh words sometimes ya know. I know someone who had his dog stolen and bred. The cops were involved. When they found the dog he was with the female and the litter had just dropped. The police decided the man who's dog was stolen, had all legal right to the pups so he took them all and did spay/neuter before they were rehomed. I'd really make sure you keep a good eye on the neighbor, shady people will do anything to make a buck.