I know exactly what you guys mean, I have had two guys crash when riding with me in the last two years.
One was a total lunitic (I didn't know him he just joined in) who ended up with serious knee and shoulder injuries crashing at 120kph in front of me on a bumpy bend who was riding like a loon including blocking me as though he was on a track. Guess what he was riding? A BMW armchair! LT1200
I saw it somersault through the trees (3 metres high) which he himself hit.
The other was a young bloke I didn't know who we met on the way who asked if could join the group of four. My mate fred and I said yes but you must ride at your own pace and not try to keep up if any of us are riding outside your comfort zone................................. yeah right!
First set of mountain twisties the guy stacks it a bit like your guy ExPatTommo.
My mates and I spent the rest of the morning helping the Fire brigade and ambos. Oil all over the road etc.
It turned out he was wearing the worm race leathers he bought second hand along with the CBR 600 with warn tyres too. (Never judge a book by it's cover). He got off with minor injuries but wrote off his bike.
I prefer to ride with a few guys I know, we all know what the other can and can't do.
I am also guilty of the occasional "red mist" episode but mostly try to just enjoy myself and mind my own business and leave others to do there own thing as long as they keep outa my way and I will get out of the way of someone obviously better or nuttier than me.
DaveM