In the public discourse about Mainland China (MLC) in Hong Kong (HK), China is usually presented as in group, and the "one-country-one-people" ideology is widely supported. In the private discourse, however, MLC is usually presented as outgroup. This article analyzes spontaneous online discussions from a chat forum where local and non-local Chinese students in an Intercultural Communication class discuss self- and other-categorizations in HK and MLC. The analyses demonstrate that a wide range of mitigation strategies is used, suggesting that students constantly engage in face-threatening activities. The data also show that HK students' stereotypes of MLC are remarkably negative, and that MLC students defend themselves by constructing counter-narratives about the rejected mother and her ungrateful child. The discussion argues that social identity is a flexible concept which constantly changes depending on context and situation, and it suggests that the students' narratives should be seen as examples of different types of discourse: a Western and an Eastern discourse with fundamentally different norms for self- and other-construction. Finally, the paper argues that only by addressing potentially painful issues, and verbalizing taboos in the strained relationship between HK and MLC, is it possible, over time, to reconcile the opposing discourses about "the other"[Copyright of Journal of Multicultural Discourses is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/17447143.2011.560670]