This article presents classroom discourse analysis as a tool for critical teacher education. It argues that such analysis can raise awareness of how teachers live out their ethical commitments in classroom-level interactions, but needs to be carefully situated. Drawing on the author's research conducted while teaching junior secondary students in Hong Kong, the article weaves classroom discourse analysis into a critical incident reflection focusing on ethical tensions that emerge from a class activity exploring dehumanisation. The activity used a pedagogy of discomfort in order to unsettle students' beliefs and practices, but in facilitating the activity, the teacher's ethic of care was also challenged.