Like I said, with books, children and teenagers have hundreds to choose from at bookstores, public libraries, and their own school library. With bookstores, the books are not filtered for profanity, publishers ship them out to different bookstores around the country. Libraries do select the books they want to carry, especially school libraries, and school libraries are usually very good at choosing books with no profanity whatsoever. But again, it is completely your child's choice when it comes to choosing a book they want to read, but don't get me wrong, parents do have a say in it, and I think they always should. But, that depends on the age of your child and the way your raise your child. Some parents choose to let their child be exposed to the real word, which includes profanity, objectionable words.
In conclusion, I do not think objectionable words or profanity in books sold or available in libraries should not be disguised in any way because getting a book, purchasing it or reading it is your choice, and parents have a say in it, so there is absolutely no reason to block out or cover the objectionable words in the book. But, with television it is very different because the television producers by law have to bleep out the objectionable words in their programs. So, with books no, and with television yes since a large fraction of day time television viewers are under the age of 18 or even 17.