Exactly.
A CD almost killed Sabo when he was younger, Sabo himself has become a rebel because of that and he even managed to become chief of staff of the RA, an organization that sees CDs as the true enemy. Not only that, but Sabo has recently declared war on CDs, not Marine or Akainu, in front of the entire world, became symbol of the Revolution doing so and last but not least Imu destroyed a nation where Sabo was.
But no, "Sabo will fight Akainu" lol.
I don't know what Oda could have done to say more clearly that Sabo will go against CDs: his story, role, fame, and even recent involvements.
Akainu is Luffy's fight.