Group psychology is completely different from the more rational, measured responses of individuals.
Gentle people who never raise their voices will sometimes participate in violence if a mob mentality develops. If there are rowdy elements, take a tough, schoolmistressy tone. This will usually be acceptable to the crowd. Reasonable people will appreciate that you need to stop people shouting, repeating themselves or bypassing the chair. You risk life, limb and ridicule if you raise controversial subjects without having a strategy to deal with them.