Few communities collapse over a single incident. It's unlikely a majority of your members will quit in disgust over one issue. Instead, they will gradually drift away.
Members won't leave if you make a single bad decision. They won't leave if there is a fight. They will tolerate a lot (but will complain about it). Anger isn't the emotion you need to worry about, it's boredom.
Members leave communities when they no longer find it interesting.
If the community no longer provokes an emotional reaction, has fresh/interesting discussions, provides useful information, or doesn't help someone satisfy their ego needs, they will leave.
Members don't quit communities, they just visit less frequency. Eventually, they don't visit at all.
This means you have many opportunities to reverse this trend. You can monitor the number of visits per member, the average time spent on the site per visit, and the number of active members in the community.
If the community begins to fade, you need a new programme of activities. You need to try new themes/topics for the community. You need to set new goals/targets for the community and interactive heavily with the regular members of the community.