If you moderate a meeting you will know the following issue: depending on the topic and the participants it may happen that discussion leaves the objective level and gets more and more personal.
As moderator you must recognize these situations and intervene when necessary. Otherwise the discussion may go in a wrong direction and isn’t useful anymore.
At some point, the discussion leaves the objective level and is no longer useful. At this moment you may ask the participants to evaluate the ongoing discussion in terms of focus on the discussion subject and goals. Ask them to evaluate the discussion by showing thumbs up or down gesture (angles in-between are allowed). From about a middle rating (thumbs horizontally) it is no longer useful to continue the discussion. In this case you should break the discussion and let the participants think and talk about the meeting process in general terms. Only if they find a consensus about the way they want to execute a proper discussion, you should switch back to main topic and continue the meeting.