At a press conference in Japan, an L2-Japanese reporter questioned an L1-Japanese politician. Although the press conference was conducted in Japanese, the politician code-switched to English during their exchange. The reporter challenged the politician's code-switching; a confrontational exchange ensued. The reporter's reaction depicts the code-switching as linguistic microaggression. Linguistic microaggressions are verbal comments focused on language use itself which intentionally or unintentionally discriminate. I analyze two data sets: the press conference data and an interview with the reporter, and a survey conducted with over 300 L2-Japanese speakers in Japan. Microanalysis of the press conference reveals linguistic microaggression and a struggle for speaker legitimacy. Qualitative thematic analysis of survey data examines L2-Japanese speakers' reactions to unwanted code-switching. Together, analysis of these data sets shows how 1) linguistic microaggression can be resisted while asserting one's own speaker legitimacy, and 2) L2-Japanese speakers can react strongly to unwanted code-switching. Few studies examine unwanted code-switching. I argue that the code-switching examined here was linguistic microaggression and was perceived as a threat to L2 speaker legitimacy. Findings contribute to research that critically examines L2 speakers' struggles in Japan and have implications for understanding L2 speaker legitimacy.