As someone who was actually annoyed by OL coddling and actually aiding those groups, I gotta throw out a defense here. There isn't really much right now to show that OL won't up and smash those same groups should they meet again. That his diplomacy was only there in that specific instance, both to keep the population of the planet out of the crossfire, and get his foot in the door. What he did basically laid the groundwork that led him straight to Starfire and Blackfire, and gave him some time to set up Tamaran's defenses without being hounded by the forces he had violently said hello to.
There isn't much to say that he won't dump a can of raid into the very Spider ship he once protected if they don't want to play ball his way. Granted, it does still gall me, what he did. But at the same time...he has achieved a goal or two, and he is perhaps on the cusp of building an army/corps.
The other thing is....I don't think he could trick the Reach like he tricked the others. Given their history with Lanterns and meatpuppet practices. I don't think they would even try to hear him out, more then they would try to lure him in, to kill/steal from.