"Remember not only to say the right thing in the right place, but, far more difficult still, to leave unsaid the wrong thing at the tempting moment." Benjamin Franklin

To follow this sage advice, one must not say bad things with company that would accept it because, sooner or later, you will say bad things among company that would be offended. This is especially true for people who try to be witty or funny. They will often immediately say something witty without considering the consequences just to make others laugh. I remember a joke that was told in my Freshman year of college. A young man, free of parental guidance at his college, started swearing because others were doing it and it was fun to say whatever you want. He came home for the first holiday (either Thanksgiving or Christmas) and at the family dinner he said "pass the (expletive) butter".