More important than trying to understand why someone does the wrong thing is to continue doing the right thing. Have faith in and live by truth. "Attain truth through speaking truth and practicing truth in all your daily actions and behavior towards others." (Sri Swami Sivananda)
This is Satya. Satya is one of the five Yamas that make up the personal code of ethics practiced in Ashtanga yoga. Being truthful in one's thought, speech, & action. According to the Vedas and later in the Yoga Sutras, "Sat means true essence, nature, spiritual essence, and character." Truth alone triumphs, not falsehood. (wiki) Speak the "Satya".