I am not sure why your normal game group is better than meetups if you have a person who gets more confrontational than you'd like there when they feel wronged. Sometimes there are emotional, mental or social problems causing these issues in groups, but there is only so much a friend can do for a friend who isn't seeing a professional about developmental or other disorders.

I have found going to more groups has exposed me to a panopoly of social strategies, behaviors, and ideas than playing with the same 5-10 people had. It has not often shocked me, but I've definitely found a few frustrating situations.

Conflicts like this this can happen at meetups, but typically loud outbursts are rarer.

GT, especially base GT, is really only for people who like watching the world burn, including their own home. I don't think your friend is that guy, and does not enjoy that idea in general.

The most common fight, by an order of magnitude, at meetups, is about analysis paralysis. Some people vastly exceed box times and people have places to go and commitments to keep. If you come with a timing cube as a backup for people going for an inconsiderate amount of time, very few conflicts happen there. They have a hard time saying both "I'm not taking a lot of time" and "I won't do that".

As for your tilt incident: in almost all these situations in gaming groups, such as to your own, the portrayl of the situation has been heavily filtered through the teller, even if the teller is cetain it hasn't. The human mind makes evaluations as part of the typical process of living, and using that to hand memories on. The very act of remembering the situation literally rewrites it again in your brain, often subtly shifting it to match the evaluation more.

At best we can do is make guesses at what is going on by exploring possibilities in a "sphere" around the portrayal, guessing what really happened in people's heads.

We could ask all sorts of things like: Has A done a lot of "stupid experiments" before in other games that caused history here? Is A chronically late making B wait around? Or was this really a first time screw up? How many seconds were you taking per adventure card in round 1? How long did B's first game of this take? Did B think A just spent 3 hours of time on this when really it would be more like 40 minutes more? Does B only get out 1x a month then someone screwing around knocked him out randomly?

But, asking all those questions isn't going to make us find a golden answer to make someone hnderstand a mind different than their own.

More often than not though, most people who bring stories like this keep telling us the same consistant narrative, and we cannot help with that; they have already painted all the boxes in and backfill (unintentionally) from there because that is how most people's minds work.

But yes, by all means go to meetups, accept some people have different lives and minds than you, and set boundaries, including who you play what with and take the consequences.

MeeplesLikeUs have an "emotional accessability" dimension they analyze games on that can help find games less likely to be upsetting. That may help for your game group.