Impossible...
... to stop anyone who decides to RDP or VPN (SSL/PPTP/IPSec) into their system of choice and then browse away. The fact that people can already download content first then play them offline hasn't caused issues before so why should accessing it live be any different?
Not the mention the fact that Club World offers "privacy" screens where you and your partner essentially has a private booth where people can see what you do.
The biggest problem won't be porn - it'll be the fact that it's impossible for anyone in cattle class to use it due to the stupid way the seats are crammed in (anyone over 5ft 5" can vouch for that) and the noise issues from the midgets that can squeeze a laptop onto their lap.