I think that guy is not such an asshole, it's understanding that he probably has a mental disease, yes it's not mentioned anywhere and probably will never be mentioned. I personally don't like the character, but I can sympathize because that's just how people with asperger's can be, especially ones that aren't followed by a professional, the ones in the higher spectrum, they will focus on something no matter what or where they are.
I might as well be very wrong but I'm saying this because I personally struggle with my asperger's and I feel a lot of his symptoms fit.
He needs help, from other people/family, if I didn't have the help, I would most likely end up dead, because I also don't have an healthy lifestyle, I'm bad with people (irl no friends but a few friends online because it's easier for me to express myself and be who I really am online) and I don't care about many things, including one that's very important, eating.