People need to understand these three categories. In brief:
1. Blasphemy is when you mock what is sacred. For the idea of blasphemy to make sense, you must start off believing something is sacred. If you believe in God, you’re there. However much you venerate Martin Luther King, you don’t have a reason to think he’s sacred. He was a man. You may think he is a hero, but that doesn’t make him a god. Making fun of him is not lese majeste; no more is making fun of Mother Theresa or George Washington or whoever your favorite historical figure may be. If you believe in the Christian, Jewish, or Moslem God, however, anybody who mocks God is committing a horrendous crime deserving of death, even if we do not choose to punish the crime ourselves and leave it to God’s justice, as we also do with adultery and many other vile offences.
Note that Christians have never, even in the Middle Ages, considered mocking the Pope, or St. Peter, or Martin Luther, to be blasphemy. It is disrespectful, but it is not blasphemy.
2. Obscenity is when you use words that crudely denote body part and actions that ought to be private, not public.
3. Political Incorrectness is when you say something that the Left thinks is bad to say, usually because it is too close to the truth. Nowadays, the Left has captured the Establishment, so it is when you say something that the Establishment– the Press, the Powerful, the Rich, and the Educated– disagrees with and takes seriously enough to fear. Note that this is not quite right— you are free to say things with which they disagree which are *further* to the left, such as calling for the seizure of private property to be divided among the poor.
I will need to expand on this, of course. Laws and customs against Blasphemy and Obscenity are justified, and those against Political Correctness are not. One question is whether the rule is designed to thwart the spread of ideas and information, or just to control the manner in which they are expressed. Another is whether the offense is greater the wittier and better phrased is the utterance. Another is whether proponents of the rule are willing to discuss the matter of the utterance themselves, or whether they themselves fear to discuss it even from their own point of view.