If Torvalds were working in the medical sector, where people can actually die because of software failures
Well, software failures in the medical field are unlikely to be caused by security holes... that's his point actually, even though it is a field which isn't suited for Linux. However Linux is mostly used in environments where the machine is handling almost only network related tasks and in this cases security is the top priority, so his point doesn't make much sense but on a pc without any kind of connection. Even for desktop use, in this day and age you can't prioritize down security when almost everyone shares financial informations through his IPV4 connection for bills and purchases.