I believe Jon waited long enough hoping the clash of egos will end because most members are mature (albeit with varying sizes of egos).
Many time it started as a reaction to "I, my, me" attitude apparent in some posts then followed by pushback by others who also ignored the interest of other members that is not to escalate the duels but better dampen it down.
The clashes did not end. So, Jon had to take action. It will be naive to think that it was not expected coming. It could have been expected within +/- an hour or two (literally)!
Jon has life beside the Fig4Fun. Fig4Fun is not for-a-profit organization but in a way a service to the fig hobby community. He can't be expected to monitor minute by minute, and some do appreciate Jon's patient way of dealing with such situation hoping patience will prevail but everything has a limit. Forum has been graciously made available and maintained by Jon for the hobby happiness of all. Jon has avoided rush reactions. He finally felt the limit has been reached and breached and so he acted.
He must have weighed the situation our time and banned the people who in his view acted-or-reacted outside the expected norms and eventually banned them. I believe Jon has earned the privilege to have room when and how to take action. He also has the good of the forum at his heart. Giving him feedback is one thing but putting undue pressure on him can be problematic. What can legally prevent him to switch the F4F off in disgust. We try to login one day and the Forum is not available. Yes, some may not care but many do care and enjoy it and wish to continue in a good atmosphere for all. Occasional misunderstanding can be cleared in decent ways.
I agree that he ban should not be permanent. A forced first sabbatical for (n to 6 ) months may be expected to serve the purpose. If the undesired attitude is resumed by the member then longer ban.
It is not the first time that egos clashes happened here. It happened before some years ago. Fortunately, the Forum stayed quiet when some with big egos left but after causing some good members to leave in disgust. Let us hope normalcy returns and stays.
It is just my opinion.