I can tell he's not being serious. Any vegan knows this asker isn't or otherwise is just pulling your leg.
It's like having a smoking neighbor (which I have right now). My apartment when I keep my windows smells like smoke half the day, it's absolutely not imagined. There isn't anything I can do about it but close my windows, but it's nice out so I like to have them open. There isn't any winning in a situation like that. Yes, it's annoying to live next to smokers, same way in your contrived situation you find it bothersome this guy's cooking meat comes your direction, but you can't get him to stop, so think before you act.