This study explores argumentation and counter-argumentation patterns emerging from a corpus of readers’ comments found below-the-line of over twenty-five online articles on the subject of incest, the current legal sanctions against it and the possibility to decriminalize consensual incestuous relations between adults in Poland. The comments have been coded line-by-line for the types of positioning and argument premises using Atlas.ti software. Using the framework for argument analysis according to underlying premises, the comments were analyzed with respect to stance taken, practical reasoning conducted, and salient rhetorical strategies applied. They are subsequently correlated with the discursive formations from which they are sourced, notably ‘genetics/eugenics’ and ‘tradition/social order’ or ‘morality’ in the case of opponents of decriminalization, and ‘science/evidence,’ ‘liberalism/progress,’ and ‘romantic love’ for the proponents. In the discussion, the explanations of the competing constructions and evaluations of incest taboo and social stigma around it are referred to larger socio-political ideologies, including conservatism, nationalism and liberalism. The study contributes to the pool of argumentative and rhetorical studies on how topical issues are being debated in the media-saturated public sphere devoid of traditional gate-keeping and access control.