While emotional abuse may, on the surface, look a bit different in platonic relationships than it does in romantic or family relationships, any type of abuse typically follows the very same relational dynamics. In every abusive relationship one of the members appears to have all, or most of the power. The person being abused is typically held emotionally captive by the abuser, by ether fear of some sort of criticism or punishment, self-harm or public embarrassment. This constant fear is what typically keeps the abused friend feeling like they are never good enough and may even deserve the kind of treatment that they are receiving.
Abusive friends, like abusive partners, at times, can seem very charming, charismatic and even caring. However it is exactly this duality and unpredictability that keeps their abused partners plugged into the relationship. The abused friend may see their friend acting in a caring manner and think to themselves that their abusive friend is clearly "not all bad". They may then begin to believe that the friend is only abusive to them, and hence their negative behaviors may somehow be their fault. The abused party may then begin to think that if only they themselves were somehow a better friend to the abuser or could provide the perfect circumstance for them to not "go off", then the abusive friend would surely turn into the “good” friend that others see and stay that way.
Clearly, every type of emotional abuse is harmful. Emotional abuse impacts people’s self esteem and feelings of power, worthiness and agency in their lives no matter who is doing the abusing! Friends of emotional abusers may feel more and more depressed and less and less worthy as human beings, since their needs, wishes and desires are always squelched for those of their friends. It is important then to recognize when the abuse is happening to us or to those around us and to take measures to ensure that everyone has the knowledge, recognition and power to choose better.
This PsychCentral article provides a thorough list of the various signs of emotional abuse in any relationship.