Unless, of course, there's some kind of mechanism that gives threads with higher engagement more prominence? That might create an incentive to have more inclusive conversations. Although that might incentivise trolling too...
EDIT: Perhaps combine the above with a reputation system, where you can see how ban-happy an original poster is. Since people don't like to waste their effort writing a reply that just gets ignored, ban-happy posters would be penalised by lack of engagement. Then platform provided moderation could just become a kind of 'meta-moderation' - basically just banning people who try to game the system (e.g. posting threads saying 'please reply so I can get my ban percentage down').
If neither party is adult enough to participate, then perhaps twitter and facebook aren’t the right places to have controversial discourse.
I could however see it leading to echo chamber threads, or sham threads where one party is deliberately providing a weak counter-argument, a bit like a fox news interview to a right wing politician.