Should we make the same argument for those who self-identify as Jews writing Holocaust articles?  The only possible rationale I could see for prohibiting self-identified pedophiles from writing articles on people claiming child abuse is that it provides right wing cranks with an opportunity to publicly attack Wikipedia.  Given the collaborative process, it certainly isn't going to make any difference in the quality of the resulting article, and most minor attracted adults editing Wikipedia aren't going to publicly announce their orientation anyway.