Transgender, non-binary, and gender-diverse (TGD) people face prejudice, which is associated with psychological distress. Guided by critical theory, in the present study we sought to identify arguments used to delegitimize TGD identities online and evaluate their contribution to TGD oppression in an American context. We conducted a thematic analysis of 495 transphobic comments on TGD-related articles obtained from Fox News, Buzzfeed, and The Hill websites. A commenter exhibited anti-TGD prejudice if they used language expressing negative affect (e.g., aversion) toward TGD people. Thematic analysis revealed 11 prejudicial themes: gender essentialism, psychological instability, put-downs, TGD as a social phenomenon, TGD as a social burden, other divergent themes, TGD as unscientific, transition as mutilation, equating TGD with other concepts, childhood transition as abuse, and TGD people are dangerous. We identify implications for the mental health of TGD people.