You're 100% correct when you say that changing venues and having the arguing parties work together had changed the tone and flow of the debate experience but I can't agree that changing context will ultimately improve an argument. I would like to discuss some things I believe to be at play here, but not mentioned.
The difference between arguing online and arguing in person can be of significant importance to how the two parties interact (argue). I will go ahead and propose that if the two parties had instantly (after your request to speak in person) transported them selves to a room and sat right in front of each other without the cookies or you even being present, even then their tone and ferocity would change from what it was online. I believe that when we are online we are no longer bound by the effects of communication between body and mind (similarly time depending on the online medium). When we are online we do not read the body language of those we are speaking with and we all know that body language makes up for a very large portion of how communication plays out.
When the two parties are instantaneously transported from their chairs to being right in front of each other they are subjected to a larger portion of their emotional consciousness then they were online. Their expectations of people and how they communicate in person becomes in affect. Those attributes of the arguing parties personalities weren't all at play when the conversation was happening online.
Their characteristics while the argument was online could even be considered as dissociative to their true personality traits. Which means, yes... Changing context will effect arguments, but I wouldn't go so far as to say it will improve one. Who knows... Maybe one of your guests had a sexual desire for cookies and so became aroused which made them care less about the topic being argued and so didn't fight back as hard as they might have online.
On a recent trip to Ireland, I gave a talk on tactics for having better arguments (video here). There's plenty in the video that's been discussed on LW before (Ideological Turing Tests and other reframes), but I thought I'd highlight one other class of trick I use to have more fruitful disagreements.
It's hard, in the middle of a fight, to remember, recognize, and defuse common biases, rhetorical tricks, emotional triggers, etc. I'd rather cheat than solve a hard problem, so I put a lot of effort into shifting disagreements into environments where it's easier for me and my opposite-number to reason and argue well, instead of relying on willpower. Here's a recent example of the kind of shift I like to make:
A couple months ago, a group of my friends were fighting about the Brendan Eich resignation on facebook. The posts were showing up fast; everyone was, presumably, on the edge of their seats, fueled by adrenaline, and alone at their various computers. It’s a hard place to have a charitable, thoughtful debate.
I asked my friends (since they were mostly DC based) if they’d be amenable to pausing the conversation and picking it up in person. I wanted to make the conversation happen in person, not in front of an audience, and in a format that let people speak for longer and ask questions more easily. If so, I promised to bake cookies for the ultimate donnybrook.
My friends probably figured that I offered cookies as a bribe to get everyone to change venues, and they were partially right. But my cookies had another strategic purpose. When everyone arrived, I was still in the process of taking the cookies out of the oven, so I had to recruit everyone to help me out.
“Alice, can you pour milk for people?”
“Bob, could you pass out napkins?”
“Eve, can you greet people at the door while I’m stuck in the kitchen with potholders on?”
Before we could start arguing, people on both sides of the debate were working on taking care of each other and asking each others’ help. Then, once the logistics were set, we all broke bread (sorta) with each other and had a shared, pleasurable experience. Then we laid into each other.
Sharing a communal experience of mutual service didn’t make anyone pull their intellectual punches, but I think it made us more patient with each other and less anxiously fixated on defending ourselves. Sharing food and seating helped remind us of the relationships we enjoyed with each other, and why we cared about probing the ideas of this particular group of people.
I prefer to fight with people I respect, who I expect will fight in good faith. It's hard to remember that's what I'm doing if I argue with them in the same forums (comment threads, fb, etc) that I usually see bad fights. An environment shift and other compensatory gestures makes it easier to leave habituated errors and fears at the door.
Crossposted/adapted from my blog.