Obama is on record (over and over and over again) stating "we're going to abide by whatever the Democratic National Committee determines is fair", and the DNC has yet to decide something that's fair.  Clinton's peeps TRIED to do the "only people who voted for me get to vote" thing, but was shut down in the courts.  (Again, not by Obama.)  

Therefore, Hillary must oppose waiving the rule, since Obama's said he'd be happy with a revote that didn't have that rule.  Q.E.D.