It is not a valid teaching if it can be proved to be false.  There are enough church historians [who have ancient documents] that can prove that women did hold clerical positions in the early church.  For example, St. Brigid of Ireland was INDEED validly consecrated a bishop by a bishop.  

But like so many other issues within the church, the Vatican wants to continue to pretend that none of this happened, none of this documentation exists.  The longer the Vatican continues to deny the truth, the more painful it will be for the entire church.  People who are highly educated in theology, scripture, and church history---do not accept without question what the hierarchy claims anymore.  The hierarchy LIED too many times.