I would fight him with his own game, if he is so addicted to porn and doesnt wish to discuss it with me i would watch my own porn let him see me watching it and enjoy myself, or just compliment the guys on it.I dont see the female body as a television to be stared at.
OP's guy is disrespecting her so play him at his own game,it could back fire and he like it more but what have you got to lose either way he will watch and enjoy but there are some men who dont like their woman watching other couples or just men playing,this guy is ignorant of his SO and her needs,if he wants to know why your watching say ''baby you watch and dont come to me so why i shouldnt i watch and get pleasure from them for me too''.
Your risk your choice...
A mistake is always forgivable, rarely excusable and always unacceptable.
Robert Fripp