1. Guy didn’t wanna fight John because even though he doesn’t show it he respects him and another big fight in Rushville isn’t good optics.
2. He still feels indebted to John for passing on the ring which led to him getting his in the first place.
It’s not hard to grasp.
Guy Gardner was willing to square up with the strongest metahuman to protect earth but let's a rookie Lantern snatch his chain and take his planet without putting up a fight