Y'know...I wouldn't ever have called it, but...it works.
It's certainly the only Corps he could possibly be a member of.
Red - while he's got a short temper, it's never developed into an actual RAGE. Orange - while he's certainly avaricious enough to wield the Orange light I doubt even he could manage to pry it from Larfleez, and he's too smart to be consumed by Larfles. Green - he's got the prerequisites, no doubt, but his utter contempt for the greenies would keep him from taking a ring, even under these circumstances. Blue - while I can't think of a particular example of him expressing it, he's exactly the personality type to hold the concept of 'hope' in utter contempt. Indigo - ...and 'compassion' isn't even on his radar. Violet - while he did seem to have some affection for Stealth at the end of the last REBELS series, when they settled down to raise the kid, 'affection' is as far as it went, clearly.
Well, if someone manages to off him, the bar for getting called up to the Black Lanterns is fairly low, so...
But someone needs to successfully KILL the mofo for that, so....