text: Because they are still forming their views on sex, men and women, relationships and the world in general. Porn makes sex seem meaningless, stereotypes men and women into certain roles, and de-values relationships, among other things.  Children might be attracted to porn for hormonal reasons, but letting them view it only shows them the nasty, dirty, unemotional part of sex.  Since it is very likely they are not getting that balanced out by watching meaningful, beautiful love-making, it would be best to not waste room in their young minds with porn.