"In order for there to be a red card on an OGSO, there must be a FOUL."
No, the law states "an offense punishable by a free kick or penalty kick".
It is not completely clear how this should be interpreted. It appears
the USSF has sent an inquiry to the IFAB over the issue. See
"MISCONDUCT AND THE OBVIOUS GOALSCORING OPPORTUNITY" on Jim Allen's site.
(M.C. it appears from Aaron's post that NFHS denial ruling may have been
intended to cover a simulated injury which causes the ref to stop the
game. In those circumstances DGF would certainly seem called for.)