When you moralize, you lecture someone about right and wrong, judging their decisions and actions. It’s just plain wrong for people to moralize! Oops.
If you know someone who complains about "kids today" and pontificates about how things were in the past, adding an opinion of the proper way to act, you're familiar with the verb moralize. At the heart of moralize is moral, from the Latin root moralis, "proper behavior of a person in society," and someone who moralizes simply wants to share their own idea of what's moral — unfortunately, they tend to do it in an overly superior way.