Perhaps I mispoke. However, he did think he was writing to an underage kid at the time because the kid told him he wouldn't be 18 until later. Yes, the IMs got worse after that I agree. Except he did say something about "just dreaming" to who he thought, at the time, was an underage kid.
The point is, however, no matter how immoral, disgusting or whatever other adjective we want to use here, what Foley did was not illegal under DC law. These kids were not underage. The age of consent in DC is age 16; Foley knew very well he wasn't doing anything illegal.
However, there is the issue of sexual harrasment that remains IMO, not to mention the general feeling tht a 52 yo shouldn't be so interested in 17/18 yo kids.