Polecats are related to the weasels and are part of the weasel family but polecats do not eat chickens.
So if you have some polecats hanging around your chicken coop or yard where chickens are the polecats will not eat the chickens nor should the polecats bother the chickens.
So there's no need to worry about the polecats eating the chickens or harming the chickens.
But you do need to keep the chickens safe from hawks including chicken hawks who can sometimes sweep down and lift the chicken into the air where it will then kill the chicken somewhere else and eat it.
You can shoot a chicken if it's trying to attack your chickens or trying to get to your chickens.