There is an example I use in my community management training courses.
In a movie magazine's community, there was a ferocious debate about the greatest film of all time. The discussion had garnered several thousand posts, members were ferociously arguing their side and criticising the choices of others.
The overzealous community moderator, worried about conflict in the community, locked the thread.
This isn't a joke, the community manager locked the most popular discussion ever to take place in the community. The community manager locked a discussion members were fiercely passionate about. The community manager locked a discussion which motivated members to check back every couple of hours to participate.
The community moderator should have sent an e-mail to the entire community asking all members to give their views on the most popular discussion ever to take place in the community.
The moderator should have used the discussion to put together a list of recommended films and asked members to vote on their favourite.
This discussion could have become a cornerstone of community activity. New members could have been asked to vote on their favourite film when they join. There could have been plenty of content about how films ranked each month/year by members. It could have been made into a sticky thread for ongoing debate – especially with the release of new films and how they match up.
It's important to know when to step back from a debate, when to encourage a debate and when to jump in and settle a conflict. Getting this wrong can do a lot of harm.