We are quite as worried about that in Australia (Aussies swear a lot), but as I see it there is a production quality cost that needs to be dealt with ether by the customer, or the quality of the the final product.
I guess if they want to remove swearing you ether have to make the final product sound awful but muting the music during the swear words or have the customer pay for a separate audio recording for vocals so they can be removed cleanly in post at more expense.
The problem I see with it if the first option is used it reduces the quality of your services, which could later reflect badly on you and your work even though it is the result of the customer.