Good post, ABetaDad!
Many men do like porn I know - I don't myself, it just doesn't do a thing for me to watch other people having sex - and although I can understand the OP's shock and initial disgust, if I were her I'd try to give myself a shake, come to terms with it and not feel it any reflecton on herself, nor a sign that her DP is disgusting - he isn't - he's just horny and it's there and a quick release.
However I do feel worried about the explosion of porn and the way young men (and girls) are seeing very extreme stuff on the net from a very young age - I can't help but think it colours their attitudes to sex and women and gives them a wrong impression - C4 Teenagers and Pornography program anyone? Boys (and girls) thought normal young women's bodies were 'saggy' and that girls could be quite scary in their demands for sex with strangers, as per your average porn film where a bored, nympho housewife drags in the postman and his mate and won't let them leave till she's thoroughly 'done'.
Imagine your DS, those of you who have them - he has you as a mother, he has a good image of women as strong, equal people with minds and rights of their own. But then at the most impressionable age, with hormones raging, he and his mates see over and over again images of girls who are just men's willing - or unwilling - toys, splayed out begging for it in every hole from several men at once (he won't be watching Petra Joy !) However good the attitudes you brought him up with, I think his own might wobble a bit.
I don't know what the answer is - extreme porn and the appetites for it are not going to go away - I just wish boys had a more vanilla start to their imaginary sexual life these days - but it's straight in at the deep end now (no pun intended!) and not a wank over gauzy half-hidden glimpses in the underwear catalogue or a 60s Playboy with soft-focus, pretty, naked women - withOUT a cucumber where no cucumber should go