Claims of abuse in my opinion are usually false. In today’s day an age anytime abuse is suspected the medical provider must report it and both social services and the police investigate the claim. If police are called and they see bruising in NYC and I think in most major cities, they are required to arrest the spouse even if the victim doesn’t want to press charges. Failure for the medical provider to report it can result in the loss of the medical provider’s license to practice. Likewise a Police Officer who fails to arrest an abuser can be lose his job.
Before you claim someone is abusive check whether in your jurisdiction, do medical providers have to report suspected abuse and if the police arrest the abusing spouse. If they do then unless you have seen these reports you are defaming them and probably guilty of Motzie Shem Ra.
The fact that you have a Heter to accept Loshon HoRa-Motzie Shem Ra this is so that you can avoid an abusive relationship but doesn’t allow you to tell anyone else. Telling someone else may result in you being guilty of Rachelos, Loshon HoRa or Motzie Shem Ra besides possibly embarrassing someone. Is it worth it?