There's an easy way to circumcise a redneck: kick his sister in the jaw.
I think that incest jokes like that are in poor taste. Do you enjoy making fun of people from the South?
Of course not. It's just a joke there.
While it's good to joke around and make people laugh, it isn't appropriate to use harmful stereotypes like Southerners having sexual relationships with their family members. Doing so puts down the character of people from the South and makes it more difficult for them to get ahead in society since people consider them to be backwards because of the stereotypes they've heard. It would be good to try to find lighter subject matters to joke about so that more people can enjoy your comedy!