As I'm not an English native speaker and because it is a common joke in France, it would have been more relevant in my mother tongue maybe... Usually, people saying "I'm not racist but.../I'm not homophobic but.../ I'm not judging you but.../...", at then, say something racist/homophobic/judge.
So it was more about the wireless mouse being actually wire mouse like the non racist guy who is actually racist.
