Bad as we often use it, is based on personal taste, the fully subjective "bad", this is often colored by the Societal "bad" (by colored i mean its influenced by the social "bad", because many either go with the crowd or stand against them no mater what the subject)
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the Societal "bad" is also subjective, but a evolving subjective where time, politics, art and sience change the view over time (i.e the issue of slavery or witch burnings, artist like Van Gough or Picasso, etc)
the true objective term "bad" is something that is in direct "challenge" to good, these are the moral issues we all have (in one form of another),i.e killing is bad (to a certain degree, for most this line is self preservation). For most, its only the moral "bad" that can be attached to actions, but for some the moral bad doesn't apply to certain things and it becomes a subjective bad (i.e hanging or torturing people of other races, stealing, touching children, etc).
I hope this made sense...