In order to ACT on the emails beyond telling Foley to cease contact with the individual in question, you would have to believe that gay men who act on their attraction to underage males are functioning under a sick compulsion which they cannot control.
For Hastert to take this position without supporting evidence of other pages or more extensive contact with one page would have been a political death sentence for him.
Even if it's true.
All of our political leaders have adopted the "blue eyes-brown eyes" model for thinking about male homosexuality. They are not open to argument or persuasion on the subject.
For Hastert to step out from this consensus and to go beyond a "no contact" order would have meant that he was treating a gay man differently than he would have treated a normal man in identical circumstances.
This, in turn, would mean that Hastert was self-identifying as a dissenter from orthodoxy on the matter of human sexuality, and a) he probably isn't a dissenter, also b) if he is, he isn't willing to commit political suicide over it.