Here are some actions thought to be wrong in some cultures and thought to be permissible in others (see IP3 490ab):

• public nakedness
• polygamy
• working on the Sabbath
• infanticide
• homosexual behavior
• eating one's dead parents

For each of these actions try to think of an argument (a sound, non-question-begging, argument) for the conclusion that that action is morally wrong or is morally permissible.

Here's an example:

1. If some behavior does not harm anyone, then that behavior is morally permissible.
2. Public nakedness does not harm anyone.
3. Therefore, public nakedness is morally permissible. (By a variation on modus ponens)