on another note though, bit more seriously, I have a mate like this (not seen him in 8 years) but he didnt like people and actively unsociable, worked nights so he wouldn't be near people, he looked like Mr Burns and he was only in his early twenties.
anyway, without elaborating too much, as I got older and working in children's social services, I had a better understanding of all the stuff that happened to him when we were in school; like he had been in and out of foster care, his mum was a maniac and beat up our headteacher, some other weird stuff went on.
he was basically living in an abusive household and this had affected him to the point where he didnt want to be around people at all and I was the only person really keeping up with him. it got to the same point though where he just wouldn't turn up to things any more and that was that. shame as he was a real nice and normal bloke once you were past the weird persona everyone else saw. could easily be labeled with autism but he was just screwed up.
just saying this as people often say stuff about being on a spectrum, but there is shit loads of neglectful and abusive parenting going on behind closed doors and it deeply affects people in adulthood. I see scores of it in my 9-5, but you would never realise if you were not aware of the extent of it.
just something to consider as your mate may have had some trauma which has lead him to behave the way he does.