Not a fan of Joe, but not once in his career did he "get hit in the head for a living".
Unless you count him doing scoring points by landing a kick here and there at a handful of Tae Kwon Do tournaments when he was in his 20s or whatever (and you shouldn't, because I don't think they were allowed to strike the head, and he wasn't doing it for a living).
Joe was/is an expert in Brazilian Jiu-Jitsu, a 100% grappling martial art, and anyone who would ever strike an opponent in the head, would no question be eliminated from the competition, and likely barred from ever participating again.
Due to this intimate knowledge of BJJ, Joe's job at the UFC was color commentary. He didn't actually fight anyone. That's not like meant as a dig, it's just the truth.
As someone who used to watch MMA back in the golden years (PRIDE NEVER DIE! Early 00s PrideFC is like nothing that has ever come before, or since. And nothing will ever match that shit again imo. Shogun's 2005 tournament run? Fucking madness), Joe was a fantastic commentator. Shit, he wasn't even a bad podcast host back then.
Dunno if he smoked too much DMT with Eddie Bravo or something, but it's a bummer to see such a previously (actually) curious and open minded man go down this path... Especially given how many young, impressionable listeners he has.