Argument by incompatibility
According to Discovering the World through Debate, an "argument by incompatiblity" is "An argument designed to reject something because it is incompatible with something else" (246).
Trapp, Robert, et al. Discovering the World through Debate: A Practical Guide to Educational Debate for Debaters, Coaches, and Judges. Third Edition. New York: IDEA Press Books, 2005.