Writing is Risk
I can't help but cringe when I see writing prompts that ask the writer to "keep it clean." Other than certain rules around basic grammar, punctuation and spelling that help ensure ideas can be conveyed clearly across audiences (and even here, there is arguably some flexibility), writing should be untethered. Good writing exists at the place where creativity and risk intersect - if there isn't some sort of fear or discomfort at play while you contemplate sharing your writing, you're doing it wrong. It's hard to be honest with yourself, let alone the world, but that authenticity is what makes writing sing - the best songs evoke strong emotion, connect people and move us to action.
This is not to say that good writing has to be full of "fucks" - obscenity, sexuality, violence and the like all have their place insofar as they further the story or characterization and help the author to build a world or setting that feels true. Many a work has been criticized for unnecessary rape, for instance, that does little to advance the plot or characters and is used more so for shock value, often offering insight into the writer's social/political views on women more than anything else. But to box someone in from the start - to tell them to keep it clean in a world that is very much the opposite - seems like a recipe for the production of writing that is superficial and half-hearted. Give me the grime and the pain any day, to remind me I am real.