Pictures/video are outlawed because it involves a minor being exploited for profit/gain, and it's just plain sick. Text is, for now, legal. Otherwise Vladimir Nabokov would have been put in jail a long time ago.
No. I agree with Mr. Gotzh's analysis.
Child pornography is illegal because: (1) it harms the child involved in the production of that particular piece of pornography; and (2) it harms other children because the production of child pornography contributes to, and enhances, the underground network within which child pornography is traded, which encourages the production of more child pornography, which harms more children.......
Fictional prose about children involved in sexual acts does not harm those interests, so the production, possession, transfer, and consumption of such material is not punishable under the law.
A good rule of thumb - if you have to ask yourself whether or not you're on a child porn site, it's probably a good time to close your browser.