Lots to unpack on that one. First, I am sorry you have to deal with opp. Usually being responsible for our own junk is job enough.
I'd probably secretly start trapping their chickens and taking them to the humane society so they can be adopted out. And I'd use the chicken wire you offered them for my garden.
It would be nice to have that conversation but sounds like you already did. If missing chickens and dead carcasses don't wake them up then obviously they won't notice Humane relocation.
Best of luck and keep us posted