Seriously, there's a reason he's not understanding, it's because you people keep trying to justify the iPad with things that apply to the laptop as well. Find something that is unique to the iPad that is not some strange "I can read stuff standing up", and maybe some of the doubters will get it.
So why are you dismissing being able to use a device while standing up as a legitimate advantage of an iPad over a laptop? My wife is a teacher, and she's been dying for something like an iPad to replace her clunky Windows tablet.. which she uses on a daily basis while teaching her classes.. and yes standing up.
I wouldn't ever consider reading a book on my laptop (sitting or standing), while I can certainly see myself reading a book on an iPad. The examples can go on and on..
Sure a laptop is capable of running any application that you can also run on a tablet. Heck, you can even use your laptop as a cell phone if you really wanted to. But the point is that many of the use cases are LESS convenient to execute on a laptop than a tablet. So yeah.. why is this so hard to comprehend?