Excuse my ignorance, but at which part of this otherwise nice story the guy's ass got kicked? It was an unexpected encounter with an important figure in computing that has been quite unknown to people, and it must've been fun, but at no point I got the impression that he got his ass kicked...
It was metaphorical ass kicking. You start to reevaluate how difficult your challenges are when you start talking to someone who invented the first internally programmable computer.
Actually, the common slang you wanted was "a kick in the ass" or less vulgarly "a kick in the seat of the pants", as in this book's title, http://www.amazon.com/dp/0060155280 . An "ass kicking" is slang for a beating.
