Different languages? I mean, a lot of governments in Europe are pretty goodly, and their governmental systems aren't all that different, so the main things that keep them apart are language and culture. Hell, I think most people want to consider themselves good, and the majority of governments are designed to do good rather than ill, but people just, y'know, disagree about things. Small things.
And that's good. Diverse cultures makes settings more fun.
But disputes can be over big things too. Imagine a lawful good society that punishes criminals by consigning them and all their offspring for three generations to slavery, selling them to families that need servants. It's eminently possible, yet morally repugnant to most people.
Imagine that Sindaire and Tennas are both goodly nations, but they can't agree on trade arrangements, and the Tennas ambassador caused a scandal last year by sleeping with the Sindaire ambassador. So when Tennas gets attacked by a larger than usual force of Goblins from the mountains, Sindaire decides to withhold assistance until Tennas agrees to certain reasonable trade stipulations. To the Sindaire mind, they're not being evil; Goblins attack all the time, and you shouldn't be expected to help your neighbor with every little problem they have, right?
