I feel these days on television mostly, the respected network/show can get away with a lot more then what they used to years ago. I do believe that if a child can see this on television at any time of the day, it is not worth the risk in my eyes.
Bad words serve no purpose. Sure they are nasty in meaning to some extent, sometimes derogatory, but we shouldn't give them a mystique by keeping them hidden from young minds. Children should come to understand what these words mean, and why they are not appropriate for use. If the children decide to use them, then that should be their choice.