I'd say that challenging one's morals is important for people within the same community. It's how we help to refine one another and thus strengthen the tribe. You're absolutely right that there are many different kinds of moral framework to choose from though and that people from "Framework A" have nothing to gain by arguing with people from "Framework B." I believe that the majority of the conflict we see in the world today stems from the fact that we're so bad at sorting ourselves into tribes of compatible people. Rather than separating into homogeneous tribes, everyone's compete with one another over the levers of centralized state power. Political correctness is also in the way because to propose such sorting is denounced as being racist, xenophobic, etc.