Bitcoin = Ponzi
So by that logic, he doesn't own anything on his hard drive just because he can't put the 1s and 0s in his pocket.
The tangibility argument, ah well.
I've tried arguing toward metalheads that bitcoin was tangible (in the spirit of sunnankars Why Bitcoin is tangible. Doesn't work, you just get accused of philosophy or word-bending.
I then tried to talk to them about why tangibility was important for preservation/guarantee of persistent ownership (because you can effectively deny access) and that this feature of tangibility was also given with bitcoin. Didn't work... Bitcoin was still "worse than fiat".
Now I have a nice counter-argument and I will say something like: "watch out, you better put your secret thoughts in your pocket quickly, otherwise I might steal them from you" (think brainwallet). I still have to work on the specifics, but thanks for the idea, Logik.
So you don't own your private thoughts?
Just ask them for what price they will sell the password and login details to their on-line bank account and/or stock-trading account, etc.
Since such details are not tangible and they cannot hold them (in their pockets or otherwise) those things must be worthless by their own logic.