Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answered 8 months ago

Gheebat (Backbiting) of a believer is a major sin. 
Regarding talking bad about non believers, we should not waste our valuable time in talking bad about others except the enemies of Allah who were been cursed by Allah and His Messenger.