Email “discussion” groups are misnamed. Email “question and answer” group is probably more accurate. Or email “disperse information” group. That’s because involved discussions are difficult to hold via an email group. To be truthful, discussions about controversial topics are difficult to manage even when people are face to face. We humans already have a strong set of core beliefs are quick to filter out all that does not appeal to us, quick to anger, and slow to change our minds.
Communication by email itself is fairly limited because you can not also convey meaning via your voice or body language. So important nuances are quickly lost.
It also takes much more time to write a clear message, than to speak it. So terse replies are common and easy to misconstrue. And it’s easy to misinterpret an email and read in anger or hatred when none was intended.
So when you hear all those stories about flame wars, they were likely a result of people “discussing” something, not just answering a question or passing along new information.