Just for the record, I kill copperheads when I find them. There are more than enough copperheads in our wild areas, and I see no purpose for them around the farm, especially with small children running around. I would also kill water moccasins if we had them, but we're in a blessed part of the country that harbors only one type of poisonous snake.
I'm not an animal rights nut, although I do believe in humane treatment for captive animals (though my definition of humane is very different from the extreme animal rights folks and includes keeping them for meat). My reason for treating our resident snakes with care is that they provide a valuable service in exchange for very little. I don't have to feed them (except an occasional quail which they harvest for themselves), don't have to provide shelter or clean water or vet care. I don't have to build cages or clean poop or worry about dietary requirements. They don't need attention or affection, walks or playtime. All I have to do is not kill them, and make sure my small animals are in secure pens. In exchange, they prevent rats and mice from eating the expensive feed and contaminating it & the surrounding areas with poop. As much as I love my livestock, I can't think of another animal on my farm that provides so much in exchange for so little. Why would I want to harm them?
On the other hand, in some instances the balance may tip the other way. If you've got a snake who has developed a taste for quail and decides to eat them exclusively or even mainly, then you've got a snake that has stopped providing a service and become a drain on your resources. In that case, it's time to terminate or relocate. I do the same with drakes that are no longer needed, or quail that are picking on other quail, etc. The only exceptions to that rule are the human animals & the pets that we keep for pure entertainment/lifestyle/affection purposes.
Oops--apparently certain specific group names are off limits here. Sorry. Edited to change the name of a group to a generic term.