The Bible talks about there being a time for this and a time for that. Is there a time for swearing? Don’t people swear?
Of course, they do! And some people, not all, swear profusely. But should a writer include swear words?
The real question is Am I able to Write in Multiple Genres?
Ultimately it is your audience that determines the answer to that. However, it is possible that you could end up with a different audience for each genre. In fact, I’d say that is likely that your audiences will change from genre to genre.
Breaking into a new genre (for you) can also be tough. In my case, my primary focus is writing good fiction no matter what the genre. Getting people to like my books is more a matter of marketing than anything else.
The agent has given you his advice and has made it clear that unless you change things as he has described, he won’t represent you. Complicating the matter is the fact that you have not been able to find another agent. What do you do?
You read any of my novels and I leave out the excessive graphics. That doesn’t mean there’s no sex, violence, or anything like that. When I write a scene I leave the excess up to the reader. Which brings up an important maxim.
The truth of the matter profanity in writing has less to do with creating “real” characters and more to being a crutch. Instead of investing time and effort into creating believable characters some authors opt for profanity and graphic text. These are crutches usually designed to cover poor writing.