1 yes moderators should be able to do whatever they feel like including ending interesting discussions.
2 no moderators should remain neutral and only end a thread if it becomes arguementative.
I have seen a number of interesting disscussions ended by moderators recently based on what appears to be nothing more than the moderator's personal oppinion that they dissagree with the topic being discussed. Should they be able to do this in your oppinion or should there be a way to moderate poor moderators who cannot remain neutral and do what they are here for?