It’s common when trying to build support for a community to pretend nothing bad will happen.
But this is going to hurt you and your community when it does. Worse yet, if you’ve pretended nothing bad will happen you probably don’t have an agreed plan to deal with the risks.
Instead of trying to pretend it won’t happen, it’s better to pretend it will.
But you need to explain three things here:
1) You’ve identified the risks. You have worked with various teams (marketing, PR, IT, legal, product to identify the most likely risks (legal, reputation, risk to members, risk to staff etc…). Invite stakeholders to add their concerns to the list.
2) You have a plan to respond and mitigate each of them. You’ve taken proactive steps to reduce the likelihood of something bad happening and have a plan to respond when it does. Invite anyone with concerns to help develop your plans here too.
3) The incredible benefits of a community far outweigh these risks. Much of the business world is shifting towards community. Control is in decline. You can figure out how to do community now or later, but at some point it will happen. The benefits of a community are too important to not pursue because of concerns about risks.
The more active your community becomes the bigger the risk that something bad will happen. On a long-enough time scale, it’s almost inevitable.
If you want to mitigate the concerns of colleagues, engage them in the journey of identifying and mitigating the risks (and identifying the benefits they need from the community).