It doesnt surprise me that there are folks that have believed this myth. It was considered such a widespread truth that many if not most churches banned the throwing of rice at weddings. What does shock me is that in the face of real truth and real evidence and logic that folks given the gift...
While there may be difference of opinion there is no disputing the fact that Rice is a perfectly good grain for feeding to poulty. It is in FACT used in some formulations. There is nothing safe or sorry associated. It seems OP wants to cook it for the birds that is great has nothing to do...
FYI on the rice, if it has been dry and is not molded or sprouted I am quite certain it is fine for anyone. If you are uneasy feed it to the birds as it is not expensive to replace. It will be fine just as you have been told.