Two wrongs fallacy
According to Discovering the World through Debate, a two wrongs fallacy "Occurs when a debater makes an argument urging the audience to accept, or condone, one thing that is wrong because another similar thing, also wrong, has been accepted and condoned" (250).
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.