(graphic via JC) I've got a copy of the full letter.
Amidst alarming reports that irresponsible theories about the events of 9/11 have begun to gain currency with the American people, you should not want to lend your personal reputation to a production which seems likely to instigate new and dangerous falsehoods. And so we ask that you use your influence to persuade ABC to withdraw the broadcast altogether. Failing that, we urge you to sever your relationship with this grossly misleading production.
Samuel R. Berger
Taylor Marsh has John Kerry's reaction