Several language dichotomies -- particularly the pervasive idea that "academic" language distinctly contrasts with "social" language -- have dominated teachers' thinking and discourse about language-related instructional practices in recent decades. Many researchers now question ramifications that binary thinking about language might have for students, particularly multilingual students and students speaking non-dominant English varieties. Teacher educators are called to challenge dichotomous thinking about language in working with teachers, and our study illuminates some of the difficulties they face in that pursuit. In this practitioner-research study, we present data from online discussions in a graduate-level linguistics in education course, in which 19 in-service teachers seeking ESL endorsements discussed an article critiquing the dichotomy of Basic Interpersonal Communication Skills (BICS) and Cognitive Academic Language Proficiency (CALP). Our question was: How do in-service teachers respond to critiques of dichotomous views of language? We used structural and descriptive qualitative coding to locate teachers' exploration of these ideas in their discussions and then examined their rationales. Our findings suggest that most teachers rejected the article's critique and instead defended BICS and CALP alongside other language dichotomies, often linking justifications to their experiences with multilingual students. We offer implications for disrupting this binary thinking through new approaches to recontextualizing teachers' knowledge.