Talking about abusive exposure to porn itself is an abuse but it is almost a given now that your kids will see it. My son had a friend of whom I disapproved -- he was sneaky and quite hostile, which is odd in a child towards his friend's mum. At the time his mother was sleeping with different men every month or so, and this clearly affected him a lot. He really didn't like women, and made a point of showing my son some really vile porn. Lots of aggression, no body hair, anal sex, three men, one woman. My poor son was only 11.
He did this on our computer, which had Net Nanny software. He got past that effortlessly, as did my older son when trying to do something which wasn't porn or anything nasty, just downloading some cartoon that the Net Nanny was set up to stop. I tried another safety software package and the children went straight past that too. Unless you are a real computer whizz and create your own barrier it's almost impossible to stop your kids getting at whatever they want on a pc. None of the packages work.
Luckily, only a week or two later, we were together late one night in just the sort of quiet relaxed situation in which children feel safe to confide. My poor son told me what he'd seen -- he was embarrassed but he managed to give me the general outline. Then we had a long talk about sex. I stressed how normal it was, and how it was a happy, affectionate affair, something loving that all couples did. I explained that anyone who tried to start their real life sex life using porn as a template would meet with disaster. He was very relieved to hear that.
I started talking about all the nice mums and dads we know, and how they all have sex. I told him that real sex was far more gentle and friendly. I can remember everything I said, but we ended up laughing at the absurd idea that the happy couple we knew were acting out the harsh, hairless aggression that the porn portrayed. I even brought up anal sex. I told him it was true that some people did it, but I stressed that unlike in porn it wasn't an expected element. Remember, the poor child was only 11, but he'd seen such nasty, unkind stuff.
It was one of the key conversations we'd had over the years. I know it really helped because he told me so years later.
He's 17 and a half now, and has a lovely girlfriend whom he treats just as I would hope. They are always laughing. They've been together all year and are now sexually active. He takes every precaution (he told me so) and I imagine that whatever they do, they do with love and affection.
I think we all have to take the bull by the horns. If you've got Internet access, your kids will have seen porn. And most of it is nasty. Watch out for social network sites and music downloads. My older son downloaded a hip hop track which came attached to a short, totally disgusting, porn clip. He was so horrified he came and got me, and we deleted it. There must be weirdos out there attaching sadistic porn to tracks that are most in demand from kids. Very unpleasant.
I am not against erotic material. There are things that could be labelled "porn" that are lovely, arousing and life-enhancing. Sexuality is an important and beautiful thing. But we have to tell our children that the ugly stuff does not represent what real people who want to make love are likely to do.
I'd suggest you wait until you're in an easy, relaxed situation with one child at a time and ask your child directly what they've seen, and how it affected them. I will never forget how relieved my son was to learn that sex in real life wasn't anything like porn. Poor child had thought that he'd have to do all this once he grew up, and didn't fancy the idea at all! :-)
Recently I had a conversation with both my sons, separately, and brought up this body hair business. The bald porn look is now so widespread that boys expect girls to remove most or all of their pubic hair. I pointed out the porn link, and said it was a fashion and one of which, as a liberal old punk, I strongly disapproved. I asked them to reject the necessity for high maintenance pubic topiary, and told them that, in my view, it was oppressive to women -- telling girls that their natural appearance in that area was unacceptable. The boys took my rant quite well. They are used to me sounding off about political and ethical issues :-)