Well I suppose the best thing you can do is what you've already done by correcting yourselves. He is obvioulsy upset at the things he's saying so its sounds like just a case of time breaking bad habits.
If you believe he has picked up this talk from you, then I would not punish him for using it as he's already punishing himself, but praise him for when he manages not to, and praise yourselves too, bad habits are hard to break. Perhaps a swear box would help, maybe the first person to go a week without putting anything in could have the contents to spend on themselves?
