In both my ‘cases’ the off-list verbal abuse I got were the two most offensive exchanges of any kind that I’ve ever had with another human being - or animal come to that. I’ve had worse with some rusty fasteners but that’s a different kind of nut.
The irony was that both would almost certainly be car buddies if they lived around the corner. Alex included me in a ignition coil deal he organized, and I offered to take him out for a drink when I was due in Menlo Park one time, but no dice.
I would speculate about some kind of personality trait but I just remembered that was one of his tactics - suggesting you had a psychiatric disorder in ‘needing’ to be right, LOL! As a lister I didn’t mind so much - it was a useful discipline in making points clearly and focused and unarguable, similar to what I did for a living at the time. But as an Admin I had to respond to complaints and when it got vile off-list I parked him for two weeks. I’d possibly handle it differently now.