For those of you who don't know (so basically the 3 luddite grandmothers following me):
Pepe the Frog is a cartoon used by fascists to signal support for the Alt Right (and other forms of fascism and nazism). Kekistan is a fascist meme that grew out of 4 chan culture. And Nazis frequently disguise their dog-whistling behind an interest in Roman history and culture, particularly centurions and the "roman salute" which is more or less a nazi salute.
Musk is saying "I'm a fascist" out loud.