A lot of people ask questions like "How should society be organized?" or "What should be done with criminals?" or make statements like "There shouldn't be censorship in the world" or "We should have a world without violence". All these thoughts show a fundamental misunderstanding of morality. Morality is inherently transitive and cannot exist from any perspective other than that of an individual agent. You can say "I should do this", or even "you should do this", but you can't say "this should be done". The only meaningful way to interpret such a statement is "everyone involved should work together to achieve this", but that statement is forgetting that each individual involved has different information and a different perspective, and so assuming that the right action from your position is necessarily the right action from everyone else's position (as the passive voice requires) is wrong. This is "intolerance" in the worst way possible: you're trying to achieve world peace by sacrificing individuality and the real meaning of morality. You want everyone to give up their own conscience and moral agency to follow your ideas. That is evil. Note the difference from Protagonism. I do not want people to ignore their own conscience for the sake of harmony with me, I want them to listen to their own conscience instead of ignoring it for the sake of harmony with society at large, as they currently do. I of course hope they will arrive at my same conclusions, but if they don't, I don't try to use the government to enforce my beliefs on everyone and even make them pay for the enforcement.
There would be some instances of conflict in a world with only very good people. It is possible that two good people could have opposing duties and thus they would have to fight and neither of them would be in the wrong. I call this situation "the moral conflict". (Some freeloading situations are a non-violent example of moral conflict.) Protagonists would understand this and take it no farther than the subject of the dispute was worth nor harbor any hard feelings over it, but I can't say the same for non-Protagonists.
To give an example of a situation where the moral conflict would definitely be taken to the point of violence, consider two good people trapped in a cave and knowing when they will be able to escape but having only enough food for one of them to survive that long. The moral course of action (for either agent) is to try to save whichever of them they think is more strategically important to the forces of good. In most cases, this will be themselves, as they're very likely to have at least some disagreement in how a person should act, but obviously both people think they have the right side of every disagreement. So if they both understood the lesson of this article, they'd fight to the death in complete good spirits and without any anger between them. (We're discounting the risk of this resulting in both of them dying.)