If a manager sends a text message to another manager about a employee’s work performance in a belittling way is that considered workplace harassment

Perhaps, but workplace harassment is not a legal claim in North Carolina.  Harassment in the workplace is unlawful only in certain situations as there is no law specifically prohibiting harassment.  Initially, we have to determine the reason he was harassed and if that reason is unlawful, he may have a claim. In this state (as in most states), workplace harassment may be unlawful only if it is directed toward the employee on the basis of: race, color, sex, national origin, religion, disability or age 40 or older.  If the alleged harassing actions were directed toward him on any other basis than one of these "protected classes", then it will not matter what the actions were because it simply will not meet the legal definition of unlawful harassment. If it is directed to him on the basis of one of these protected classes, it will be unlawful only if it occurs on mulitple occasions.