[Agrippa]

It depends on the issue and persons in question, as well as on other factors involved. F.e. one agent provocateur can destroy and otherwise constructive discussion by making a debate "heat" in an irrational way.

For some issues there can be no meaningful discussion since the positions are clear and there are arguments for both - so it will be rather a list of arguments for either case, either parties, enemies and end with insults. This might be, however, be helpful and interesting for those not involved in that debate so far.

And not to forget, in many cases you dont know how it ends when it begins. I had discussions with people which ended surprisingly constructive and friendly and others which I thought about being rather harmless first ending in a rather "harder way".

I voted for No. 2.