In addition to the things mentioned above (which are all good suggestions) there are a couple of other tools at your disposal:
Staff notices
Add a staff notice into the topic that says something along the lines of “Hey guys, things are getting a little heated here. Please be kind and keep things on track or this topic will be closed.” That lets people know that you’re watching.
Encourage flagging
Encourage a culture of flagging. That empowers your community to drive the kind of behaviour that they want to see. If you start seeing a number of flags in a particular topic then there’s your sign that things aren’t cool.