Under the laws of all states in this country, the court under each state's statutes is entitled to order a person convicted of certain crimes such as the one you have written about (malicious mischief/trespass) to attend anger management as well as other therapeautic classes.Seemingly this is what you were ordered to attend as part of the sentence you received for trespass. The purpose of the course is to show to the court that you have attended a process required under state statute.