Warren Buffet writes to his Directors:

Sometimes your associates will say “Everybody else is doing it.” This rationale is almost always a bad one if it is the main justification for a business action. It is totally unacceptable when evaluating a moral decision. Whenever somebody offers that phrase as a rationale, in effect they are saying that they can’t come up with a good reason. If anyone gives this explanation, tell them to try using it with a reporter or a judge and see how far it gets them.