I am encouraged by the community's response to the problem, and hope the first two posters will note not only the number of respondents against porn but the quality of those respondents, since here you have some of the most helpful posters in WordPress. And note as well that they did not take some kind of no-porn-for-minors-only position, either. Porn has no place in civilized society, because it is unfriendly to love. Just to name one effect.
Nor is it true that porn is legal. This is a dodge, based on confusion. It is similar to the confusion that exists around privacy protection. We saw the results of this confusion in the Virginia Tech shootings; the young shooter had shown clear signs of enormous problems, but had not been restrained because it was assumed that the discussion among the educational professionals in his life was illegal, when in face this is not the case. It is the same with pornography. It is not legal, it is terribly harmful, it has been associated with many manifestations of severe social maladjustment, it makes a hostile environment for women (especially on the internet!), and maybe worst of all, it is boring. But presently these laws are difficult to enforce due to the misrepresentation to the public about their exercise, and the failure of people to protest its use.
Porn is the absence of sexuality, according to a survey conducted in Japan by a large condom manufacturer, which found that the more an individual 'used' porn, the less actual physical relationship they enjoyed with other human beings (I have a blog about this that cites the study). Due to the lack of intercourse, Japan is disappearing.
If you persist in his good education, Daniel has a chance to have an appropriate reaction to pornography when he is twelve, and twenty: disgust and dismay. Please continue to take steps to keep porn out of his life.