I summarize where we are when things get very busy or it appears that we are reaching a position or a conclusion. If I step in on-list, it usually stops the discussion and the issue remains unresolved. I've noticed the same thing on other lists. Eventually, the unhappy listers go form another list fragmenting the group. It's too complicated to participate in all five and participation is seen as taking sides anyway.
Reactions cause much more off-topic and unproductive discussion than any direct statements.
I deal with reactors off list. I assure other listers who alert me off-list that I am dealing with it, stay cool. These two principles seem to work. Just like meetings, email discussions, particularly ones intended to reach agreements, need facilitation. I recently successfully negotiated a flame war that involved charges of racism, sexism, stupidity, and un-American activities.