Just noticed this, but ajb seems to substitute naughty words all by itself.
Nice idea, but the main problem is when the naughty word isn't so naughty, for instance;
The male equivalent of a hen would be a c**k. A c**k usually lives on a farm, when they peck at grain and seeds spread in the yard. Sometimes while foraging for food, the c**k will inadvertently spread its seed around by scraping it with its feet.
Many people like animals, especially down the farm. Cows, sheep, goats and a c**k all live together happily. A farmer near me has a big c**k which he lets run round his yard. His wife feeds it, but she doesn't enjoy it when the farmers c**k wakes her up early in the morning. She says it's always up early and if it wakes her up early again, she'll shoot the farmers c**k with the 12 bore and then put it in the oven.