Nigeria is a multi-ethnic, multi-cultural, and multi-religious society confronted with different crises. The social media have also become important part of Nigerians. They offer a digital space for free speech and opinions. The open nature of social media platforms affords Nigerians the privilege to discuss national issues and present their opinions. However, those discussions often turn toxic, damaging the sanity of social media platforms. Nevertheless, not much research effort has been directed towards unravelling the connection between violent and biased Facebook posts or comments and ethno-religious crises. Consequently, social media communication has continued to generate crises and aggravate those caused by other factors. Therefore, this study analysed Nigerian netizens’ Facebook posts and comments on national news to identify lexical and rhetorical violence capable of escalating crises in Nigeria. The main objectives of the research were to identify lexical items and rhetorical devices that are violent and biased in netizens’ posts and comments on the Facebook and underscore the role of critical literacy in addressing the challenge of verbal violence in social media discourses. The study adopted Ethno-linguistic Identity Theory (EIT) and Politeness Theory as theoretical framework. Posts and comments that constitute violent and biased representations in public discourses were purposively selected from the Facebook to provide data for the study. Findings showed that netizens use Facebook posts and comments to drive targeted animosity, transmit biases and polarize a large number of Nigerian users through some abusive, inflamed and violent lexical and rhetorical devices. They deploy a range of lexical and rhetorical choices that inflict harm, incite or heighten conflicts among Nigerian digital citizens. The Lexico-rhetorical toxicity manifests in the form of offensive expressions, ad hominem, sarcasm, pejorative jokes, sweeping statements, condescension, dehumanization, stereotyping, discerning attribution, superfluous representations, sweeping generalisation, negative lexicalisation, name-calling, verbal bullying, insult and threats. The study underscores the need for critical literacy, effective moderation policies and mediations to mitigate the impact of linguistic violence and promote positive and respectful interactions in the digital space.