nycbusdriver
Veteran
Porno on airplanes happens more than you would think. Most people are fairly discreet, but you will get the occasional person holding up and looking at the centerfold. And, I've seen several x-rated movies on a personal computer, as well as x-rated photos.
As you say, most are discrete.
Also, as you point out, there are X-rated movies/videos resident in the memory of some folks' computers already. How would a software block on the WiFi connection help that? How would the software block on the WiFi connection keep the occasional dweeb from opening up the centerfold of a nudie magazine? (Rhetorical questions not necessarily directed at you.)
Short answer: It won't help.
Then why be concerned at all with internet porn on the airplanes?