Excellent observation.
Consider two street gangs fighting over the same neighborhood. They may be enemies, but that does not put them on opposite ends of the political spectrum.
Reminds me of "Life of Brian", with the "Judean People's Front" and the "People's Front of Judea", essentially the same thing but both groups hated each other. The first group the Bolsheviks killed in the Soviet Union were the other Socialists, not the Monarchists (although they eventually got around to them as well)