For me, the difference here is that while raccoons are wild, the chickens belong to someone and are property (or livestock, depending on state definitions). I would talk to a Sheriff about what could be done. Around me, they are the folk who have the most experience with how to handle situations like this. Heck, they might have a better understanding of the full situation.
My neighbor who lives on the corner has a nice flock of leghorns and a very nice coop. His run left a lot to be desired, a flimsy one layer of 3 ft chickenwire with no top. Mostly his chickens free range. Nobody in the neighborhood minded until they started going into the road. On our small street, we have five new teenaged drivers. One day after school, one of them almost got rearended as she was turning into our street. The chickens were scattered all over the road and she didn't want to run over them. The car behind her that was going straight was no doubt following her too closely and going too fast.
So as a result, Gabby's mom went to talk to the neighbor. He was very apologetic and we have not seen his flock in the road. He also added that should they get in the road again, he would rather lose a chicken than have an accident be caused by them.
The OP says the people they are dealing with are not nice, reasonable chicken owners. Since he says he has already talked to them and they do not keep their chickens home, I agree that he is within his rights to do whatever is necessary. I, for one, vote for a silent solution and love the idea of chicken fricasse.
I opt for avoiding pain and suffering whenever there is an alternative.
If the OP is still with us (?), if your sense is that they are not being cared for, you could call rescue groups, 4-H, or similar and see if they can help round up the birds and care for them properly ........ I don't know what the situation is there but maybe the birds aren't getting enough to eat and are seeking what they need where they can get it.....
And/or, if the boundary they are crossing to get to you is not unmanagably large, maybe you could just tack in along the border very simple garden fencing in no time flat - temporary, lightweight, easy.......that way they will likely stay out of your yard and no one gets hurt.