Sean, I would agree with you.
If this FO's attitude was a little less abrasive, maybe it wouldn't seem so bad. A lot of Airbus manuals are on the company laptops, so using a laptop in the cruise cannot be disallowed completely. The issue is regarding personal use.
Personally, I would rather keep mentally simulated by keeping busy, even if it means using my personal laptop, whereas some guys like to stare at the instruments as though in a trance.