HD - I guess I am talking about someone who is an addict. Someone who can't just "scratch an itch" and wander off, but someone who would keep scratching and scratching, wondering all while what they were doing because the itch went long ago it was now bleeding!
As someone said below, it's different to other addictions, because there is no obvious destruction going on (drinking -> violence/physical degeneration etc, gambling -> money down the tube).
Because it is possible to have a relaxed one off the wrist, no harm done etc, it is, I suspect, difficult for someone to spot it when they've gone over the line into excessive use. Next thing you know, it's not relaxed at all, it's a compulsion, and it's eroding their marriage.
This is, of course, all aside from the whole moral debate around the industry etc.
SAS - I wonder if you want to get your bloke to a really good family therapist. Sounds like he's imprisoned somewhere in his head, that sex is just a part of something bigger going on. Wish I could remember the name of a week-long therapy residential therapy course that a mate (with mother problems) mentioned a year back. Apparently they spend a week as a group, and course facilitators take them through their whole family set-up/disappointments/communication styles etc. But they don't just dwell on it all, they come out the other side too!
Can't think of a better present for your new LO than a dad who's done the heavy lifting to get past his reliance on and habit of porn.
Do want me to research, to see if I can get the course name?