Yes, for several reasons. First of all, you are better off not harming anyone, intentionally or accidentally. Secondly, written statements that damage someone's reputation are called libel, and spoken ones are called slander. While not illegal, they can open you up to a lawsuit and damages in civil court. If what you say or write is the truth, then you will ultimately be protected under the law, but it is an expensive process and a road you don't want to go down.
Yet writing about your own experience is valuable to you and to others. Here are some things you can do:
- change the names
- change some unimportant aspects of the situation so that it is not easy for anyone to identify the person you are talking about
Of course, sometimes, this is not possible. If someone wants to write publicly about being a survivor of child abuse, then people will suspect the parents. In these cases, a private journal, or writing under a pseudonym, or writing fiction may be the best course of action.