I think your father in law was entirely justified, given the situation you've described. He sounds like a responsible pet owner who did what he thought he needed to do to save a beloved pet. If anybody should have been punished, it should have been the irresponsible neighbor who let his aggressive dog run loose through the neighborhood.In a lot of places your father in law would have been on the right side of the law in doing what he did.
While it's usually unlawful to kill someone's pet just for being on your property, there are frequently exceptions for animals that are attacking people or domestic animals, provided you kill them during the attack (not as retribution later on). Local statutes may differ, but I'm surprised your FiL got in so much trouble for this. Was he actually arrested for killing the dog, or something tangential (like discharging a firearm in a residential area)?
Where (if you don't mind me asking) did this take place? I'm never happy to hear about pets being killed, but if it came down to it, I would kill an animal to save my own pet on my own property. I'd have to believe the other animal was really out to kill my pet to bring myself to do it.
I'd also have to feel like there was no way I could safely separate the two. I'd probably start with yelling, and if the hose was around, I'd try to scare the dog off by squirting it. If I had a gun, I would fire a warning shot before shooting the dog (hopefully the noise would scare it off).
As for trying to physically separate them, it would depend on the situation. My mother once rescued her cat from two dogs by wading in between them and kicking them away while yelling. Frankly, it's always seemed a little foolhardy to me--she's a small lady, and they were big dogs she hadn't seen before.
Nobody else was around. If the dogs had turned on her, things could have ended badly. If it had been smaller dogs, or a neighbor's dogs that had never been aggressive toward people before, I would probably have chanced it too.
As it was, I wouldn't have gone in unarmed. In a situation like your FiL's, the best thing would have been to get animal control involved early on before things escalated to this point. I realize that's not always a practical solution (particularly if you live in the country where people don't always view unattended dogs wandering around as a problem).
However, if there's a paper trail somewhere with someone official that indicates you think your neighbor's dog is a potentially vicious nuisance and you've been trying to deal with the situation peaceably, that can be helpful in proving your actions were justified if you end up injuring or killing the animal defending yourself or your property later on.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.