Are they justified in what they do?
Someone should found a new corp of lanterns named the Troll Lantern Corps.
It would be like the relationship between a Green and Blue lantern. A red lantern is always more powerful in the presence of a Troll lantern because...
They really only want justice as they have been so unjustly treated ... but when that rage consumes the person they destroy everything around them, its a very good metaphorical example of how revenge and anger can go too far and make you into somewhat a monster.
Well, I feel that they have the right to be angry. Each member of the Red Lantern Corp has suffered some sort of tragedy that left them with nothing to rely on but rage. And in most, if not all, cases it seems that the circumstances justified their putting on the rings and being consumed by anger (particularly Atrocitus and Bleez). All of that being said, that doesn't necessarily justify the steps that the Red have taken in pursuit of vengeance.